C++ Primer 第五版 部分课后题答案
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当时刚学C++的时候买了这本书，一开始前面看的一知半解，索性就先缓缓，等学完学校的C++课程（中途自己也写了不少c++的代码），一段时间之后又拿起这本书去看，感觉还是挺有滋味的，这本书对我印象中的C++做了很大的扩展，个人认为这本书不太适合刚学C++就去看，而是写了一定的代码，对C++有一个大体的了解之后再去看会很有味道。在看书的过程中自己也写了上面的课后练习题，现在整理一下，也跟大家分享一下，下面是9~12 15~16章的课后题编程题的答案
（第八章之前的都没保存/(ㄒoㄒ)/~~）：
当时保存的时候是按节保存的,比如 练习9.3、练习9.4 练习9.5、练习9.6 是在9.2.1节练习里面的题
9.2.1节练习：
<span style="font-size:18px;">#include <iostream> #include <vector> std::vector<int>::iterator fun(std::vector<int>::iterator isb,std::vector<int>::iterator ise,int y){ while(isb<ise) if(*(isb)==y) return isb; else isb++; return ise; } int main() { std::vector<int> s={1,2,3}; std::vector<int>::iterator is=s.begin(); //if(fun(is,s.end(),2)) cout<<"OK"<<endl; is=fun(is,s.end(),2); std::cout<<*is<<std::endl; while(std::cout<<*is<<"#" && (is++)<s.end()); return 0; } </span>
9.3.1节练习：
#include <iostream>
#include <vector>
#include <list>
#include <deque>
int main()
{
std::string temp;
std::deque<std::string>dq;
for(int i=1;i<=3;++i){
std::cin>>temp;
dq.push_front(temp);
}
auto x=dq.begin(); //std::deque<std::string>::iterator x;
while(x < dq.end() && std::cout<<" "<<*(x++));
std::cout<<std::endl;
std::list<std::string>l;
for(int i=1;i<=3;++i){
std::cin>>temp;
l.push_front(temp);
}
auto y=l.begin();
while(y!=l.end() && std::cout<<" "<<*(y++)); //list中无 > <操作 使用!=代替
std::cout<<std::endl;
return 0;
}
9.3.3节练习：
#include <iostream>
#include <vector>
#include <list>
#include <deque>
int main()
{
int ia[]={0,1,1,2,3,5,8,13,21,55,89};
std::vector<int > vec={0,1,1,2,3,5,8,13,21,55,89};
std::list<int > lis={0,1,1,2,3,5,8,13,21,55,89};
auto i=vec.begin();
while(i!=vec.end())
if(*i % 2)i=vec.erase(i);
else i++;
auto j=lis.begin();
while(j!=lis.end())
if(*j % 2==0)j=lis.erase(j);
else j++;
for(auto x:vec) std::cout<<" "<<x;
std::cout<<std::endl;
for(auto x:lis) std::cout<<" "<<x;
std::cout<<std::endl;
return 0;
}
9.5.3节练习：
练习9.47：
#include <iostream>
#include <algorithm>
int main()
{
std::string temp("ab2c3d7R4");
std::string digit("0123456789");
std::string word;
for(int i=0;i<24;++i){
word+=(char)('a'+i);
word+=(char)('A'+i);
}
std::string::size_type pos=0;
while((pos=temp.find_first_of(word,pos))!=std::string::npos) std::cout<<temp[pos++];std::cout<<std::endl;
pos=0;
while((pos=temp.find_first_of(digit,pos))!=std::string::npos) std::cout<<temp[pos++];std::cout<<std::endl;
pos=0;
while((pos=temp.find_first_not_of(digit,pos))!=std::string::npos) std::cout<<temp[pos++];std::cout<<std::endl;
pos=0;
while((pos=temp.find_first_not_of(word,pos))!=std::string::npos) std::cout<<temp[pos++];std::cout<<std::endl;
return 0;
}
练习9.49:
#include <iostream>
int main()
{
std::string temp("bdfghijklpqty");
std::string s;
while(std::cin>>s){
std::string::size_type pos=0;
while((pos=s.find_first_not_of(temp,pos))!=std::string::npos)std::cout<<s[pos++];
std::cout<<std::endl;
}
return 0;
}
练习9.50：
#include <iostream>
#include <vector>
int main()
{
std::vector<std::string > vec={"1","2","3","4","5"};
int sum1=0;
for(auto x:vec) sum1+=stoi(x); //codeblock（12.11）报错，vs2012也报，本汪编译器不支持
std::cout<<sum1<<std::endl;
double sum2=0.0;
for(auto x:vec) sum2+=stod(x);
std::cout<<sum2<<std::endl;
return 0;
}
练习9.51：
#include <iostream>
class A{
public :
A(const std::string s="10/12/1994"){
std::string sign=" ,/";
auto pos=s.find_first_of(sign);
month=s.substr(0,pos);
day=s.substr(pos+1,s.find_first_of(sign,pos+1)-pos-1);
year=s.substr(s.find_last_of(sign)+1);
}
void print(){
std::cout<<month<<" "<<day<<" "<<year<<std::endl;
}
private:
std::string year,day,month;
};
int main()
{
A a;
a.print();
A b("jan 1/1990");
b.print();
return 0;
}
/*
#include <iostream>
#include <vector>
#include <list>
#include <deque>
#include <algorithm>
#include <numeric>
#include <cstring>
using namespace std;
int main()
{
int a1[]={1,2,3,4,5,6};
int a2[sizeof(a1)/sizeof(a1)];
auto ret=copy(begin(a1),end(a1),begin(a2));
return 0;
}
*/
练习10.1：
#include <iostream>
#include <vector>
#include <list>
#include <deque>
#include <algorithm>
using namespace std;
int main()
{
std::vector<int > vec={1,2,3,4,5,6,7,12,3,4,6,7,3,6,9,2,6,3,3,3,3,3,3};
std::cout<<count(vec.begin(),vec.end(),3)<<std::endl;
std::list<std::string > lis={"q","e","sdg","zvgs","123g","545","qwe","uyt","qwe"};
std::cout<<count(lis.begin(),lis.end(),"qwe")<<std::endl;
return 0;
}
10.2.1节练习：
/*
#include <iostream>
#include <vector>
#include <list>
#include <deque>
#include <algorithm>
using namespace std;
class A{
public :
A(const string s="1/1/1990"):month("jan"),day("1"),year("1994"){
string sign=" ,/";
auto pos=s.find_first_of(sign);
month=s.substr(0,pos);
day=s.substr(pos+1,s.find_first_of(sign,pos+1)-pos-1);
year=s.substr(s.find_last_of(sign)+1);
}
void print(){
cout<<month<<" "<<day<<" "<<year<<endl;
}
private:
string year,day,month;
};
int main()
{
A a();
a.print();
// A b("1/1/1990");
// b.print();
return 0;
}
*/
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
int main()
{
std::vector<int > vec={1,2,3,4,5,6,7,8,9};
std::cout<<accumulate(vec.cbegin(),vec.cend(),0)<<std::endl;
std::vector<std::string > vec_str={"a","b","c","d"};
std::cout<<accumulate(vec_str.cbegin(),vec_str.cend(),std::string(""))<<std::endl;
//accumulate(,,"");错误 const char* 没有定义+操作
//accumulate(,,"hello"); 最后结果是 helloxxxx
char *s=(char *)malloc(10*sizeof(char));
char s1[]="heheda",s2[]="heheda";
std::cout<<std::equal(s1,s1+strlen(s1),s2)<<std::endl;
return 0;
}
10.2.2节练习：
#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
#include <numeric>
int main()
{
//10.6
int num[]={1,2,3,4,5,6};
std::fill_n(std::begin(num),std::end(num)-std::begin(num),0);
for(auto x:num) std::cout<<x<<" ";
std::cout<<std::endl;
//10.7 a
std::vector<int > vec;
std::list<int >lst;
int i;
while(std::cin>>i) lst.push_back(i);
std::copy(lst.cbegin(),lst.cend(),back_inserter(vec)); //vec未申请空间，所以使用插入迭代器
for(auto x:vec) std::cout<<x<<" ";
std::cout<<std::endl;
//10.7 b
std::vector<int > vecc;
vecc.reserve(10);
//虽然分配了内存 但size()=0 vecc.begin()==vecc.end() capacity()=10
std::fill_n(vecc.begin(),10,0);
for(auto x:vecc) std::cout<<x<<" ";
std::cout<<std::endl;
return 0;
}
10.2.3节练习：
#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
#include <numeric>
void elimDups(std::vector<std::string > &vec){
std::sort(vec.begin(),vec.end());
auto uni=std::unique(vec.begin(),vec.end()); //把重复单词忘末尾放，返回指向不重复范围的后一个迭代器
vec.erase(uni,vec.end());
for(auto x:vec) std::cout<<x<<" ";
std::cout<<std::endl;
}
int main()
{
std::vector<std::string> vec={"the","quick","red","fox","jumps","over","the","slow","red","turtle"};
elimDups(vec);
return 0;
}
// the quick red fox jumps over the slow red turtle
10.3.1节练习：
#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
#include <numeric>
void elimDups(std::vector<std::string > &vec){
std::sort(vec.begin(),vec.end());
auto uni=std::unique(vec.begin(),vec.end()); //把重复单词忘末尾放，返回指向不重复范围的后一个迭代器
vec.erase(uni,vec.end());
for(auto x:vec) std::cout<<x<<" ";
std::cout<<std::endl;
}
bool isShortter(std::string a,std::string b){
return a.size()<b.size();
}
bool islessfive(const std::string &a){
return a.length()<5;
}
int main()
{
std::vector<std::string> vec={"the","quick","red","fox","jumps","over","the","slow","red","turtle"};
elimDups(vec);
std::stable_sort(vec.begin(),vec.end(),isShortter);
for(auto x:vec) std::cout<<x<<" ";
std::cout<<std::endl;
auto iter=partition(vec.begin(),vec.end(),islessfive);
while(iter!=vec.end())std::cout<<*iter++<<" ";
std::cout<<std::endl;
return 0;
}
// the quick red fox jumps over the slow red turtle
10.3.2节练习：
练习10.16：
#include <iostream>
#include <vector>
#include <algorithm>
void elimDups(std::vector<std::string > &vec){
std::sort(vec.begin(),vec.end());
auto uni=std::unique(vec.begin(),vec.end()); //把重复单词忘末尾放，返回指向不重复范围的后一个迭代器
vec.erase(uni,vec.end());
std::cout<<"after unique_sort and erase :"<<std::endl;
for(auto x:vec) std::cout<<x<<" ";
std::cout<<std::endl;
}
int main()
{
//10.15
int x,y;
std::cin>>x>>y;
auto fun2=[x](const int y){return x+y;};
std::cout<<fun2(y)<<std::endl;
//10.16
std::vector<std::string> vec={"the","quick","red","fox","jumps","over","the","slow","red","turtle"};
elimDups(vec);
std::stable_sort(vec.begin(),vec.end(),[](const std::string &a,const std::string &b){return a.size()<b.size();});
std::cout<<"after stable_sort:"<<std::endl;
for(auto x:vec) std::cout<<x<<" ";
std::cout<<std::endl;
int n;
std::cin>>n;
auto iter=find_if(vec.begin(),vec.end(),
[n](const std::string &s){
return s.size()>=n;
});
auto count=vec.end()-iter;
for_each(iter,vec.end(),[](const std::string &s){std::cout<<s<<" ";});
std::cout<<std::endl;
return 0;
}
练习10.18：#include <iostream>
#include <vector>
#include <algorithm>
void elimDups(std::vector<std::string > &vec){
std::sort(vec.begin(),vec.end());
auto uni=std::unique(vec.begin(),vec.end()); //把重复单词忘末尾放，返回指向不重复范围的后一个迭代器
vec.erase(uni,vec.end());
std::cout<<"after unique_sort and erase :"<<std::endl;
for(auto x:vec) std::cout<<x<<" ";
std::cout<<std::endl;
}
int main()
{
std::vector<std::string> vec={"the","quick","red","fox","jumps","over","the","slow","red","turtle"};
elimDups(vec);
stable_sort(vec.begin(),vec.end(),[](const std::string &a,const std::string &b){return a.size()<b.size();});
std::cout<<"after stable_sort:"<<std::endl;
for(auto x:vec) std::cout<<x<<" ";
std::cout<<std::endl;
int n;
std::cin>>n;
auto iter=partition(vec.begin(),vec.end(),
[n](const std::string &s){
return s.size()<n;
});
auto count=vec.end()-iter;
for_each(iter,vec.end(),[](const std::string &s){std::cout<<s<<" ";});
std::cout<<std::endl;
return 0;
}
10.3.3节练习：
#include <iostream>
#include <vector>
#include <algorithm>
int main()
{
std::vector<std::string> vec={"the","quick","red","fox","jumps","over","the","slow","red","turtle"};
auto x=count_if(vec.begin(),vec.end(),[](const std::string &s){
return s.size()>=6;});
std::cout<<x<<std::endl;
int y=0;
auto def=[=]()mutable{
if(y==0) return true;
else{
--y;
return false;}
};
return 0;
}
10.3.4节练习：
#include <iostream>
#include <vector>
#include <functional>
#include <algorithm>
using namespace std::placeholders; // bind_n操作
bool check_size(const int &x,std::string::size_type sz){return x>=sz;}
int main()
{
std::vector<int > vec={1,3,6,8,0,3,5,12,4,2};
std::string s="woqu";
auto f=bind(check_size,_1,s.size());
for(auto x:vec)
if(f(x)){
std::cout<<x<<std::endl;
break;
}
return 0;
}
10.4.1节练习：
#include <iostream>
#include <list>
#include <vector>
#include <functional>
#include <algorithm>
int main()
{
//10.27
std::list<int > lst={1,2,2,2,2,2,2,2,6,8};
std::list<int > lst1;
unique_copy(lst.begin(),lst.end(),back_inserter(lst1));
std::cout<<"old array:";
for_each(lst.begin(),lst.end(),[](const int &x){std::cout<<x<<" ";});
std::cout<<std::endl;
std::cout<<"new array:";
for_each(lst1.begin(),lst1.end(),[](const int &x){std::cout<<x<<" ";});
std::cout<<std::endl;
//10.28
//其中front_inserter报错 ?inserter 复制失败
std::vector <int > vec={1,2,3,4,5,6,7,8,9};
std::vector <int > front_vec,back_vec,rand_vec;
auto iter=vec.begin();
//copy(vec.begin(),vec.end(),front_inserter(front_vec));
copy(vec.begin(),vec.end(),back_inserter(back_vec));
copy(vec.begin(),vec.end(),inserter(vec,iter));
// std::cout<<"front:";
//for_each(front_vec.begin(),front_vec.end(),[](const int &x){std::cout<<x<<" ";});
std::cout<<std::endl;
std::cout<<"back:";
for_each(back_vec.begin(),back_vec.end(),[](const int &x){std::cout<<x<<" ";});
std::cout<<std::endl;
std::cout<<"rand:";
for_each(rand_vec.begin(),rand_vec.end(),[](const int &x){std::cout<<x<<" ";});
std::cout<<std::endl;
return 0;
}
10.4.2节练习：
#include <iostream>
#include <vector>
#include <iterator>
#include <fstream>
#include <algorithm>
//10.33
void fun(const std::string &inf_file,const std::string &outf1_file,const std::string &outf2_file){
std::ifstream inf;
inf.open(inf_file);
std::istream_iterator<int > inf_iter(inf),eof;
std::ofstream outf1;
outf1.open(outf1_file);
std::ofstream outf2;
outf2.open(outf2_file);
std::ostream_iterator<int > outf1_iter(outf1),outf2_iter(outf2);
while(inf_iter!=eof){
if((*inf_iter)%2) outf1<<*inf_iter;
else outf2<<*inf_iter;
inf_iter++;
}
std::cout<<"从文件\""<<inf_file<<"\"中读取数字，奇数已存入\""<<outf1_file<<"\"中，偶数已存入\""<<outf2_file<<"\"中"<<std::endl;
inf.close();
outf1.close();
outf2.close();
}
int main()
{
//10.29
std::ifstream inf;
inf.open("test.txt");
std::istream_iterator<std::string > in_iter(inf); //in_ter 从文件流inf中读取类型为std::string的值
std::istream_iterator<std::string > eof; //文件结束位置
std::vector<std::string> vec(in_iter,eof); //把文件的字符串读入vec中
auto iter=vec.begin();
while(iter!=vec.end()) std::cout<<*iter++<<" ";
std::cout<<std::endl;
inf.close();
//10.30
std::istream_iterator<int > in(std::cin); //in从输入流cin中读取类型为int的值
std::istream_iterator<int > eof2; //输入流结束位置
std::vector<int > vec2(in,eof2); //输入的数据读入vec2
sort(vec2.begin(),vec2.end()); //排序
std::ostream_iterator<int > out(std::cout," "); //把类型为int的值写到输出流out中，每个值后加空格
copy(vec2.begin(),vec2.end(),out);//vec2的值读出到out中
std::cout<<std::endl;
std::ostream_iterator<int > out2(std::cout," ");
unique_copy(vec2.begin(),vec2.end(),out2); //不重复的复制
std::cout<<std::endl;
//10.33
fun("num_in.txt","num_out1.txt","num_out2.txt");
return 0;
}
10.4.3节练习：
#include <iostream>
#include <vector>
#include <iterator>
#include <algorithm>
#include <list>
int main()
{
//10.34 10.35
std::vector <int > vec={1,2,3,4,5,6,7,8,9};
std::vector<int >::reverse_iterator reiter=vec.rbegin(); //反向迭代器
while(reiter!=vec.rend()) std::cout<<*reiter++<<" ";
std::cout<<std::endl;
std::vector<int >::iterator iter=vec.begin(); //普通迭代器
while(iter!=vec.end()) std::cout<<*iter++<<" ";
std::cout<<std::endl;
//10.36
std::list<int > lis={1,2,3,0,6,4,0,1,3,2}; //查找最后一个0，返回其迭代器
std::list<int >::reverse_iterator lis_reiter=find(lis.rbegin(),lis.rend(),0);
std::cout<<*lis_reiter<<std::endl;
//10.37
std::vector <int > vec2={1,2,3,4,5,6,7,8,9,10}; // 取其中 3~7 的位置复制给std::list
std::list <int> lis2;
auto vec2_iter=vec2.begin();
copy(vec2_iter+2,vec2_iter+7,back_inserter(lis2));//后插迭代器实现
for(auto x:lis2) std::cout<<x<<" ";
std::cout<<std::endl;
return 0;
}
11.1.1节练习：
#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
//algorithm提供的string转换字母大小写函数写法
std::string fun(std::string &s){
transform(s.begin(),s.end(),s.begin(), ::tolower);
std::string s2;
for(auto x:s) if(islower(x)) s2+=x; //去标点
return s2;
}
int main()
{
std::map<std::string ,size_t > m;
std::string word;
while(std::cin>>word && word!="end") m[fun(word)]++;
for(const auto &x:m)
std::cout<<x.first<<" : "<<x.second<<std::endl;
return 0;
}
11.2.1节练习：
#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
int main()
{
std::map<std::string ,std::vector<std::string > > name;
std::string first_name,last_name;
while(std::cin>>first_name>>last_name && first_name!="end")
(name[first_name]).push_back(last_name);
for(auto x:name){
std::cout<<x.first<<": "<<std::endl;
for(auto y:x.second) std::cout<<y<<" ";
std::cout<<std::endl;
}
return 0;
}
/*
李 胜
李 冰冰
李 连杰
刘 韶
刘 氓
刘 星
刘 亦菲
张 三丰
张 天泽
张 晓红
end e
*/
11.2.3节练习~练习11.12、练习11.13：
#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
#include <map>
int main()
{
//11.12 11.13
std::vector <std::pair<std::string ,int> > vec1,vec2,vec3;
std::pair<std::string ,int> pa;
while(std::cin>>pa.first>>pa.second){
vec1.push_back({pa.first,pa.second});
vec2.push_back(std::pair<std::string,int>(pa.first,pa.second));
vec3.push_back(pa);
}
for(auto x:vec1) std::cout<<x.first<<" "<<x.second<<std::endl;
return 0;
}
练习11.14：
#include <iostream>
#include <vector>
#include <algorithm>
#include <utility> //pair
#include <map>
int main()
{
//11.14
std::map<std::string ,std::vector<std::pair<std::string,std::string> > > name;
std::string first_name;
std::pair<std::string,std::string> last_name;
while(std::cin>>first_name>>last_name.first>>last_name.second && first_name!="end")
(name[first_name]).push_back(last_name);
for(auto x:name){
std::cout<<x.first<<": "<<std::endl;
for(auto y:x.second) std::cout<<y.first<<" "<<y.second<<" ";
std::cout<<std::endl;
}
return 0;
}
11.3.2节练习：
#include <iostream>
#include <algorithm>
#include <map>
int main()
{
//11.20
std::map<std::string ,size_t > word_count;
std::string word;
while(std::cin>>word && word!="end"){
std::pair< std::map<std::string ,size_t>::iterator,bool> ite=word_count.insert({word,1});
if(!ite.second) ite.first->second++;
}
for(auto x:word_count)
std::cout<<x.first<<" : "<<x.second<<std::endl;
//11.23
std::multimap<std::string ,std::string> name;
std::string first_name,last_name;
while(std::cin>>first_name>>last_name && first_name!="end")
name.insert({first_name,last_name});
for(auto x:name)
std::cout<<x.first<<": "<<x.second<<std::endl;
return 0;
}
11.3.5节练习：
#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <utility>
int main()
{
//11.31
std::multimap<std::string ,std::string > book={{"oyy","c++ prime"},
{"oyy","java plus"},
{"oyy","english"},
{"awei","math"},
{"awei","computer"},
{"baobao","taijiong"},
{"baobao","gangjiong"},
};
std::string find_name="baoba";
auto ite=book.find(find_name);
while(ite!=book.end() && ite->first==find_name){
ite=book.erase(ite);
}
for(auto x:book) std::cout<<x.first<<" "<<x.second<<std::endl;
return 0;
}
11.3.6节练习：
#include <iostream>
#include <map>
#include <fstream>
#include <sstream>
int main()
{
//11.33
//读取转换规则
std::ifstream readfile("test1.txt");
std::map<std::string ,std::string> tran;
std::string word_first,word_second,temp;
while(readfile>>word_first && getline(readfile,word_second))
tran[word_first]=word_second.length()==0?word_first:word_second.substr(1);
//读取要转的内容
std::ifstream readfile2("test2.txt");
std::string sentc,word;
while(getline(readfile2,sentc)){
std::istringstream in(sentc);
while(in>>word){
if(tran.find(word)!=tran.end()) std::cout<<tran[word]<<" ";
else std::cout<<word<<" ";
}
std::cout<<std::endl;
}
return 0;
}
/*
test1.txt
brb be right back
k okay?
justkey
y why
r are
u you
pic picture
thk thanks!
l8r later
test2.txt
where r u
y dont u send me a pic
k thk l8r
*/
12.1.1节练习：
#include <iostream>
#include <vector>
#include <initializer_list>
#include <memory>
#include <stdexcept>
//12.2
class StrBlob{
typedef std::vector<std::string> vstring;
public:
StrBlob():data(std::make_shared<vstring>()){}
StrBlob(std::initializer_list<std::string > lis):data(std::make_shared<vstring>(lis)){}
vstring::size_type size()const {return data->size();}
void push_back(const std::string &s){data->push_back(s);}
void pop_back(){
check(0,"pop on empty StrBlob");
data->pop_back();
}
std::string &front(){
check(0,"front on empty StrBlob");
return data->front();
}
std::string &back(){
check(0,"back on empty StrBlob");
return data->back();
}
private:
std::shared_ptr<vstring> data; // emory
void check(vstring::size_type i,const std::string &s)const {
if(data->size()<=i) throw std::out_of_range(s); // stdexcept
}
};
int main()
{
//12.1
StrBlob b1{};
{
StrBlob b2={"a","an","the"};
b1=b2;
b2.push_back("about");
}
std::cout<<b1.back()<<std::endl;
StrBlob b3{"wo","qu"};
std::cout<<b3.back()<<std::endl;
return 0;
}
12.1.2节练习：
#include <iostream>
#include <vector>
#include <memory>
//12.6
std::vector<int > *new_vecint(){
return new std::vector<int>;
}
void read_data(std::istream &in,std::vector<int> *&pv){ //普通指针 引用指针
int x;
in>>x;
pv->push_back(x);
}
void print(std::vector<int> *&pv){
for(auto x:*pv) std::cout<<x<<" ";
std::cout<<std::endl;
delete(pv);
pv=nullptr;
}
//12.7
std::shared_ptr <std::vector<int > > ptr_vecint(){ //智能指针
return std::make_shared<std::vector<int > > ();
//return shared_ptr<vector<int >> (new vector<int>(p));
}
void ptr_read_data(std::istream &in,std::shared_ptr<std::vector<int > > &spv){
int x;
in>>x;
spv->push_back(x);
}
void ptr_print(std::shared_ptr<std::vector<int > > spv){
for(auto x:*spv) std::cout<<x<<" ";
std::cout<<std::endl;
}
int main()
{
//12.6
auto pv=new_vecint();
for(int i=1;i<=3;++i) read_data(std::cin,pv);
print(pv);
//12.7
auto spv=ptr_vecint();
for(int i=1;i<=3;++i) ptr_read_data(std::cin,spv);
ptr_print(spv);
return 0;
}
12.1.6节练习：
#include <iostream>
#include <vector>
#include <initializer_list>
#include <memory>
#include <stdexcept>
#include <fstream>
#include <sstream>
class StrBlob{
typedef std::vector<std::string> vstring;
public:
friend class StrBlobPtr;
StrBlob():data(std::make_shared<vstring>()){}
StrBlob(std::initializer_list<std::string > lis):data(std::make_shared<vstring>(lis)){}
vstring::size_type size()const {return data->size();}
void push_back(const std::string &s){data->push_back(s);}
void pop_back(){
check(0,"pop on empty StrBlob");
data->pop_back();
}
std::string &front(){
check(0,"front on empty StrBlob");
return data->front();
}
std::string &back(){
check(0,"back on empty StrBlob");
return data->back();
}
private:
std::shared_ptr<vstring> data; // memory
void check(vstring::size_type i,const std::string &s)const {
if(data->size()<=i) throw std::out_of_range(s); //stdexcept
}
};
//12.19 12.20
class StrBlobPtr{
typedef std::vector<std::string> vstring;
public :
StrBlobPtr():curr(0){}
StrBlobPtr(StrBlob &a,size_t sz=0):wptr(a.data),curr(sz){}
std::string &deref() const {
auto p=check(curr,"dereference past end");
return (*p)[curr];
}
StrBlobPtr& incur(){
check(curr,"increment past end of StrBlobPtr");
++curr;
return *this;
}
bool empty(){
if(curr < wptr.lock()->size()) return false;
return true;
}
private:
std::shared_ptr<vstring> check(size_t i,const std::string &msg)const {
auto ret=wptr.lock();
if(!ret) throw std::runtime_error("unbound StrBlobPtr");
if(ret->size() <= i)
throw std::out_of_range(msg);
return ret;
}
std::weak_ptr<vstring> wptr;
size_t curr;
};
int main()
{
//12.20
std::ifstream in("in.txt");
std::string word_s;
StrBlob sb;
while(getline(in,word_s)){ //从文件读入数据
std::stringstream sin(word_s);
std::string word;
while(sin>>word) sb.push_back(word);
sb.push_back("\n");
}
StrBlobPtr sbp(sb); //使用StrBlob 指针类型输出StrBlob
while(!sbp.empty()){
std::cout<<sbp.deref()<<" ";
sbp.incur();
}
return 0;
}
/*
in.txt
i think we should do it if you don't mind.
so what do you want to do?
*/
12.2.1节练习：
#include <iostream>
#include <memory>
#include <algorithm>
#include <cstring>
#include <iterator>
int main()
{
//12.23
char sc1[]="woqu",sc2[]=" nimeide";
char *q=new char[strlen(sc1)+strlen(sc2)+1];
strcpy(q,sc1);
strcat(q,sc2);
std::cout<<q<<std::endl;
std::string s1="woqu",s2=" nimeide";
std::cout<<s1+s2<<std::endl;
delete [] q;
// need to tell the size. 12.24
std::cout << "How long do you want the string? ";
int size(0);
std::cin >> size;
char* input = new char[size + 1]();
std::cin.ignore(); //读取多余回车
std::cout << "input the string: ";
std::cin.get(input, size + 1);
std::cout << input;
delete[] input;
return 0;
}
12.2.2节练习：
#include <iostream>
#include <memory>
//12.26
int main()
{
int n;
std::cout<<"please input size:";
std::cin>>n;
std::cin.ignore();
std::allocator<std::string > t; //定义类型对象
auto const p = t.allocate(n); //申请内存
auto q=p;
std::string word;
while(q!=p+n && std::cin>>word) t.construct(q++,word); //调用构造函数
while(q!=p){
std::cout<<*--q<<std::endl;
t.destroy(q); //调用析构函数,释放对象
}
t.deallocate(p,n); //释放内存
return 0;
}
12.3.1节练习：
#include <iostream>
#include <map>
#include <vector>
#include <set>
#include <memory>
#include <sstream>
#include <fstream>
//12.28
typedef std::vector<std::string >::size_type line;
int main()
{
std::vector<std::string > text;
std::map<std::string ,std::set<line> > sign;
std::string file_name;
std::cout<<"enter file name : "<<std::endl;
std::cin>>file_name;
std::cin.ignore();
std::ifstream file_input(file_name);
std::string senten,word;
while(getline(file_input,senten)){ //读入文件内容
text.push_back(senten);
std::stringstream word_in(senten);
line len=text.size();
while(word_in>>word) sign[word].insert(len);
}
while(true){ //查询
std::cout<<"enter the query word and enter q to quit : ";
std::cin>>word;
std::cin.ignore();
if(word=="q") break;
auto loc=sign.find(word);
if(loc==sign.cend()) std::cout<<"not find "<<word<<std::endl;
else {
std::cout<<word<<" : "<<std::endl;
for(auto x:loc->second)
std::cout<<"(line "<<x<<") : "<<text[x-1]<<std::endl;
}
}
return 0;
}
12.3.2节练习：
练习12.30：
#include <iostream>
#include <map>
#include <vector>
#include <set>
#include <memory>
#include <sstream>
#include <fstream>
//12.30 同12.27
class TextQuery;
class QueryResult;
using line=std::vector<std::string>::size_type;
//文件查询类，存错整个文件内容 以及每个单词出现的行数 定义查询函数返回一个查询结果类
class TextQuery{
public :
//构造函数 获取一个文件输入对象 构造 sign p_text
TextQuery(std::ifstream& in):p_text(new std::vector<std::string >){
std::string senten; //读取每行的句子
while(getline(in,senten)){
p_text->push_back(senten);
auto len=p_text->size();
std::stringstream word_in(senten);
std::string word;
while(word_in>>word){
auto isok=sign.find(word);
//若该单词还为出现过，申请新的空间
if(isok==sign.cend()) sign[word].reset(new std::set<line>);
sign[word]->insert(len);
}
}
}
//该函数的定义必须在QueryResult 完整定义后定义，这里只做声明
QueryResult query(const std::string &s)const ;
private :
std::shared_ptr<std::vector<std::string > > p_text; //存内容
std::map<std::string,std::shared_ptr<std::set<line> > > sign; //存每个单词所在行位置数
};
//查询结果类 包括查询的单词 以及该单词所在的所有行数 单词所在行的句子(即必须获取所有内容)
class QueryResult{
private:
std::string word; //查询的单词
std::shared_ptr<std::set<line> > p_line; //该单词的行号
std::shared_ptr<std::vector<std::string> >p_text; //存句子
public :
//print要使用里面的成员
friend std::ostream& print(std::ostream& out,const QueryResult& qr);
QueryResult(std::string s,
std::shared_ptr<std::set<line> > pl,
std::shared_ptr<std::vector<std::string> > pv):
word(s),p_line(pl),p_text(pv){}
};
QueryResult TextQuery::query(const std::string &s)const{
std::shared_ptr<std::set<line> > null_ptr(new std::set<line> );
auto isok=sign.find(s);
//若未找到，返回第二个参数为新申请的初始化的空间
if(isok==sign.cend()) return QueryResult(s,null_ptr,p_text);
else return QueryResult(s,isok->second,p_text);
}
std::ostream& print(std::ostream& out,const QueryResult &qr){
out<<qr.word<<" : "<<std::endl;
for(auto x:*qr.p_line) out<<"(line "<<x<<" ): "<<qr.p_text->at(x-1)<<std::endl;
return out;
}
void runQueries(std::ifstream &infile){
TextQuery tq(infile);
while(true){
std::cout<<"enter word to look for, or q to quit: ";
std::string s;
if(!(std::cin>>s) || s=="q") break;
print(std::cout,tq.query(s))<<std::endl;
}
}
int main()
{
std::ifstream in("in.txt");
runQueries(in);
return 0;
}
练习12.32：
#include <iostream>
#include <map>
#include <vector>
#include <set>
#include <memory>
#include <sstream>
#include <fstream>
#include <stdexcept>
//12.32
class StrBlob{
typedef std::vector<std::string> vstring;
public:
StrBlob():data(std::make_shared<vstring>()){}
StrBlob(std::initializer_list<std::string > lis):data(std::make_shared<vstring>(lis)){}
vstring::size_type size()const {return data->size();}
void push_back(const std::string &s){data->push_back(s);}
void pop_back(){
check(0,"pop on empty StrBlob");
data->pop_back();
}
std::string &front(){
check(0,"front on empty StrBlob");
return data->front();
}
std::string &back(){
check(0,"back on empty StrBlob");
return data->back();
}
std::string at(int x){
return data->at(x);
}
private:
std::shared_ptr<vstring> data; // emory
void check(vstring::size_type i,const std::string &s)const {
if(data->size()<=i) throw std::out_of_range(s); // stdexcept
}
};
class TextQuery;
class QueryResult;
using line=std::vector<std::string>::size_type;
//文件查询类，存错整个文件内容 以及每个单词出现的行数 定义查询函数返回一个查询结果类
class TextQuery{
public :
//构造函数 获取一个文件输入对象 构造 sign p_text
TextQuery(std::ifstream& in):p_text(new StrBlob){
std::string senten; //读取每行的句子
while(getline(in,senten)){
p_text->push_back(senten);
auto len=p_text->size();
std::stringstream word_in(senten);
std::string word;
while(word_in>>word){
auto isok=sign.find(word);
//若该单词还为出现过，申请新的空间
if(isok==sign.cend()) sign[word].reset(new std::set<line>);
sign[word]->insert(len);
}
}
}
//该函数的定义必须在QueryResult 完整定义后定义，这里只做声明
QueryResult query(const std::string &s)const ;
private :
std::shared_ptr<StrBlob > p_text; //存内容
std::map<std::string,std::shared_ptr<std::set<line> > > sign; //存每个单词所在行位置数
};
//查询结果类 包括查询的单词 以及该单词所在的所有行数 单词所在行的句子(即必须获取所有内容)
class QueryResult{
private:
std::string word; //查询的单词
std::shared_ptr<std::set<line> > p_line; //该单词的行号
std::shared_ptr<StrBlob >p_text; //存句子
public :
//print要使用里面的成员
friend std::ostream& print(std::ostream& out,const QueryResult& qr);
QueryResult(std::string s,
std::shared_ptr<std::set<line> > pl,
std::shared_ptr<StrBlob > pv):
word(s),p_line(pl),p_text(pv){}
};
QueryResult TextQuery::query(const std::string &s)const{
std::shared_ptr<std::set<line> > null_ptr(new std::set<line> );
auto isok=sign.find(s);
//若未找到，返回第二个参数为新申请的初始化的空间
if(isok==sign.cend()) return QueryResult(s,null_ptr,p_text);
else return QueryResult(s,isok->second,p_text);
}
std::ostream& print(std::ostream& out,const QueryResult &qr){
out<<qr.word<<" : "<<std::endl;
for(auto x:*qr.p_line)
out<<"(line "<<x<<" ): "<<qr.p_text->at(x-1)<<std::endl;
return out;
}
void runQueries(std::ifstream &infile){
TextQuery tq(infile);
while(true){
std::cout<<"enter word to look for, or q to quit: ";
std::string s;
if(!(std::cin>>s) || s=="q") break;
print(std::cout,tq.query(s))<<std::endl;
}
}
int main()
{
std::ifstream in("in.txt");
runQueries(in);
return 0;
}
练习12.33：
#include <iostream>
#include <map>
#include <vector>
#include <set>
#include <memory>
#include <sstream>
#include <fstream>
//12.30 同12.27
class TextQuery;
class QueryResult;
using line=std::vector<std::string>::size_type;
//文件查询类，存错整个文件内容 以及每个单词出现的行数 定义查询函数返回一个查询结果类
class TextQuery{
public :
//构造函数 获取一个文件输入对象 构造 sign p_text
TextQuery(std::ifstream& in):p_text(new std::vector<std::string >){
std::string senten; //读取每行的句子
while(getline(in,senten)){
p_text->push_back(senten);
auto len=p_text->size();
std::stringstream word_in(senten);
std::string word;
while(word_in>>word){
auto isok=sign.find(word);
//若该单词还为出现过，申请新的空间
if(isok==sign.cend()) sign[word].reset(new std::set<line>);
sign[word]->insert(len);
}
}
}
//该函数的定义必须在QueryResult 完整定义后定义，这里只做声明
QueryResult query(const std::string &s)const ;
private :
std::shared_ptr<std::vector<std::string > > p_text; //存内容
std::map<std::string,std::shared_ptr<std::set<line> > > sign; //存每个单词所在行位置数
};
//查询结果类 包括查询的单词 以及该单词所在的所有行数 单词所在行的句子(即必须获取所有内容)
class QueryResult{
private:
std::string word; //查询的单词
std::shared_ptr<std::set<line> > p_line; //该单词的行号
std::shared_ptr<std::vector<std::string> >p_text; //存句子
public :
//print要使用里面的成员
friend std::ostream& print(std::ostream& out,const QueryResult& qr);
QueryResult(std::string s,
std::shared_ptr<std::set<line> > pl,
std::shared_ptr<std::vector<std::string> > pv):
word(s),p_line(pl),p_text(pv){}
std::set<line >::iterator begin(){ //begin
return p_line->begin();
}
std::set<line >::iterator end(){ //end
return p_line->end();
}
std::shared_ptr<std::vector<std::string> > get_file(){ //get_file
return p_text;
}
};
QueryResult TextQuery::query(const std::string &s)const{
std::shared_ptr<std::set<line> > null_ptr(new std::set<line> );
auto isok=sign.find(s);
//若未找到，返回第二个参数为新申请的初始化的空间
if(isok==sign.cend()) return QueryResult(s,null_ptr,p_text);
else return QueryResult(s,isok->second,p_text);
}
std::ostream& print(std::ostream& out,const QueryResult &qr){
out<<qr.word<<" : "<<std::endl;
for(auto x:*qr.p_line) out<<"(line "<<x<<" ): "<<qr.p_text->at(x-1)<<std::endl;
return out;
}
void runQueries(std::ifstream &infile){
TextQuery tq(infile);
while(true){
std::cout<<"enter word to look for, or q to quit: ";
std::string s;
if(!(std::cin>>s) || s=="q") break;
print(std::cout,tq.query(s))<<std::endl;
}
}
int main()
{
return 0;
}
15.2.1节练习：
#include <iostream>
//15.3
class Quote{
public :
Quote()=default;
Quote(const std::string &book,double sales_price):bookNo(book),price(sales_price){}
std::string isbn()const {return bookNo;}
virtual double net_price(std::size_t n) const {return n*price;}
friend double print_total(std::ostream&,const Quote&,size_t );
private:
std::string bookNo;
protected:
double price=0.0;
};
double print_total(std::ostream &os,const Quote &item,size_t n){
double ret=item.net_price(n);
os<<"isbn: "<<item.isbn()<<" sold :"<<n<<" total due: "<<ret<<std::endl;
return ret;
}
int main()
{
Quote q("c++ prime",150);
print_total(std::cout,q,3);
return 0;
}
15.2.2节练习：
#include <iostream>
#include <cstdio>
//15.5 15.6 15.7
class Quote{
public :
Quote()=default;
Quote(const std::string &book,double sales_price):bookNo(book),price(sales_price){}
std::string isbn()const {return bookNo;}
virtual double net_price(std::size_t n) const {return n*price;}
friend double print_total(std::ostream&,const Quote&,size_t );
private:
std::string bookNo;
protected:
double price=0.0;
};
class Bulk_quote:public Quote{
public :
Bulk_quote()=default;
Bulk_quote(const std::string &book,double sales_price,std::size_t num,double disc):
Quote(book,sales_price),min_num(num),discount(disc){};
double net_price(std::size_t n) const{
if(n>=min_num) return n*price*discount;
else return n*price;
}
private:
std::size_t min_num;
double discount;
};
class huodong_quote:public Quote{
public :
huodong_quote()=default;
huodong_quote(const std::string book,double sales_price,std::size_t num,double disc):
Quote(book,sales_price),max_num(num),discount(disc){}
double net_price(std::size_t n)const {
if(n<=max_num) return n*price*discount;
else return net_price(max_num)+(n-max_num)*price;
}
private:
double discount;
size_t max_num;
};
double print_total(std::ostream &os,const Quote &item,size_t n){
double ret=item.net_price(n);
os<<"isbn: "<<item.isbn()<<" sold :"<<n<<" total due: "<<ret<<std::endl;
return ret;
}
int main()
{
Bulk_quote b("math",20,5,0.5);
print_total(std::cout,b,4);
print_total(std::cout,b,5);
huodong_quote h("高数",20,5,0.5);
print_total(std::cout,h,5);
print_total(std::cout,h,6);
return 0;
}
15.3节练习：
#include <iostream>
#include <cstdio>
//15.11 debug()
class Quote{
public :
Quote()=default;
Quote(const std::string &book,double sales_price):bookNo(book),price(sales_price){}
std::string isbn()const {return bookNo;}
virtual double net_price(std::size_t n) const {return n*price;}
friend double print_total(std::ostream&,const Quote&,size_t );
virtual void debug(){
std::cout<<"类成员及类型如下所示:"<<std::endl;
std::cout<<"string : bookNo"<<std::endl;
std::cout<<"double : price"<<std::endl;
}
private:
std::string bookNo;
protected:
double price=0.0;
};
class Bulk_quote:public Quote{
public :
Bulk_quote()=default;
Bulk_quote(const std::string &book,double sales_price,std::size_t num,double disc):
Quote(book,sales_price),min_num(num),discount(disc){};
double net_price(std::size_t n) const{
if(n>=min_num) return n*price*discount;
else return n*price;
}
void debug()override{
Quote::debug();
std::cout<<"size_t : min_num"<<std::endl;
std::cout<<"double : discount"<<std::endl;
}
private:
std::size_t min_num;
double discount;
};
class huodong_quote:public Quote{
public :
huodong_quote()=default;
huodong_quote(const std::string book,double sales_price,std::size_t num,double disc):
Quote(book,sales_price),max_num(num),discount(disc){}
double net_price(std::size_t n)const {
if(n<=max_num) return n*price*discount;
else return net_price(max_num)+(n-max_num)*price;
}
void debug()override{
Quote::debug();
std::cout<<"size_t : max_num"<<std::endl;
std::cout<<"double : discount"<<std::endl;
}
private:
double discount;
size_t max_num;
};
double print_total(std::ostream &os,const Quote &item,size_t n){
double ret=item.net_price(n);
os<<"isbn: "<<item.isbn()<<" sold :"<<n<<" total due: "<<ret<<std::endl;
return ret;
}
int main()
{
Bulk_quote b("math",20,5,0.5);
huodong_quote h("数学",20,5,0.5);
b.debug();
std::cout<<std::endl;
h.debug();
return 0;
}
15.4节练习：
#include <iostream>
#include <cstdio>
//15.15 15.16
class Quote{
public :
Quote()=default;
Quote(const std::string &book,double sales_price):bookNo(book),price(sales_price){}
std::string isbn()const {return bookNo;}
virtual double net_price(std::size_t n) const {return n*price;}
friend double print_total(std::ostream&,const Quote&,size_t );
private:
std::string bookNo;
protected:
double price=0.0;
};
double print_total(std::ostream &os,const Quote &item,size_t n){
double ret=item.net_price(n);
os<<"isbn: "<<item.isbn()<<" sold :"<<n<<" total due: "<<ret<<std::endl;
return ret;
}
class Disc_quote:public Quote{
public :
Disc_quote()=default;
Disc_quote(const std::string &book,double sales_price,std::size_t n,double disc):
Quote(book,sales_price),off_num(n),discount(disc){}
double net_price(size_t)const =0; //´¿Ð麯Êý
protected:
size_t off_num;
double discount;
};
class Bulk_quote:public Disc_quote{
public :
Bulk_quote()=default;
Bulk_quote(const std::string &book,double sales_price,std::size_t num,double disc):
Disc_quote(book,sales_price,num,disc){};
double net_price(std::size_t n) const override{
if(n>=off_num) return n*price*discount;
else return n*price;
}
};
class huodong_quote:public Disc_quote{
public :
huodong_quote()=default;
huodong_quote(const std::string book,double sales_price,std::size_t num,double disc):
Disc_quote(book,sales_price,num,disc){}
double net_price(std::size_t n)const override{
if(n<=off_num) return n*price*discount;
else return net_price(off_num)+(n-off_num)*price;
}
};
int main()
{
Bulk_quote b("高数",20,5,0.5);
huodong_quote h("线代",20,5,0.5);
print_total(std::cout,b,6);
print_total(std::cout,h,6);
return 0;
}
15.5节练习：
#include <iostream>
#include <cmath>
//15.21 15.22
class Graph{
public :
Graph()=default;
Graph(double x):r(x){}
virtual double get_area()=0;
virtual double get_value()=0;
protected:
double r;
const double Pi=3.1415926;
};
class Grid:public Graph{
public :
Grid()=default;
Grid(double x):Graph(x){}
double get_area(){return r*r;}
double get_value(){return 0.0;}
};
class Circle:public Graph{
public :
Circle()=default;
Circle(double x):Graph(x){}
double get_area(){return Pi*r*r;}
double get_value(){return 0.0;}
};
class Ball:public Graph{
public :
Ball()=default;
Ball(double x):Graph(x){}
double get_area(){return 4.0*Pi*r*r;}
double get_value(){return 4.0*Pi*r*r*r/3.0;}
};
class Cone:public Graph{
public :
Cone()=default;
Cone(double x,double y):Graph(x),height(y){}
double get_area(){return Pi*r*r+Pi*r*sqrt(height*height+r*r);}
double get_value(){return Pi*height*r*r/3.0;}
protected:
double height;
};
int main()
{
Grid g(2.0);
Circle ci(2.0);
Ball b(2.0);
Cone co(2.0,3.0);
std::cout<<"Grid : "<<g.get_area()<<" m^2 "<<g.get_value()<<" m^3 "<<std::endl;
std::cout<<"Cirle : "<<ci.get_area()<<" m^2 "<<ci.get_value()<<" m^3 "<<std::endl;
std::cout<<"Ball : "<<b.get_area()<<" m^2 "<<b.get_value()<<" m^3 "<<std::endl;
std::cout<<"Cone : "<<co.get_area()<<" m^2 "<<co.get_value()<<" m^3 "<<std::endl;
return 0;
}
15.7.3节练习：
#include <iostream>
//15.26
class Quote{
public :
Quote()=default;
Quote(const std::string &book,double sales_price):bookNo(book),price(sales_price){
std::cout<<"Quote construct "<<std::endl;
}
Quote(const Quote &qu){
this->bookNo=qu.bookNo;
this->price=qu.price;
std::cout<<"Quote copy "<<std::endl;
}
std::string isbn()const {return bookNo;}
virtual ~Quote(){
std::cout<<"Quote delete"<<std::endl;
}
private:
std::string bookNo;
protected:
double price=0.0;
};
class Bulk_quote:public Quote{
public :
Bulk_quote()=default;
Bulk_quote(const std::string &book,double sales_price,std::size_t num,double disc):
Quote(book,sales_price),min_num(num),discount(disc){
std::cout<<"Bulk_quote construct "<<std::endl;
};
Bulk_quote(const Bulk_quote &bkq):Quote(bkq){
this->min_num=bkq.min_num;
this->discount=bkq.discount;
std::cout<<"Bulk_quote copy "<<std::endl;
}
virtual ~Bulk_quote(){
std::cout<<"Bulk_quote delete "<<std::endl;
}
private:
std::size_t min_num;
double discount;
};
int main()
{
Bulk_quote b("math",20,5,0.5);
Bulk_quote bb(b);
return 0;
}
/* 首位两行为b调用构造函数及析构函数， 中间四行为bb调用拷贝函数及析构函数
Quote construct
Bulk_quote construct
Quote copy
Bulk_quote copy
Bulk_quote delete
Quote delete
Bulk_quote delete
Quote delete
*/
15.8节练习：
#include <iostream>
#include <cstdio>
#include <vector>
#include <memory>
//15.28 15.29
class Quote{
public :
Quote()=default;
Quote(const std::string &book,double sales_price):bookNo(book),price(sales_price){}
std::string isbn()const {return bookNo;}
virtual double net_price(std::size_t n) const {return n*price;}
friend double print_total(std::ostream&,const Quote&,size_t );
private:
std::string bookNo;
protected:
double price=0.0;
};
class Bulk_quote:public Quote{
public :
Bulk_quote()=default;
Bulk_quote(const std::string &book,double sales_price,std::size_t num,double disc):
Quote(book,sales_price),min_num(num),discount(disc){};
double net_price(std::size_t n) const{
if(n>=min_num) return n*price*discount;
else return n*price;
}
private:
std::size_t min_num;
double discount;
};
double print_total(std::ostream &os,const Quote &item,size_t n){
double ret=item.net_price(n);
os<<"isbn: "<<item.isbn()<<" sold :"<<n<<" total due: "<<ret<<std::endl;
return ret;
}
int main()
{
std::vector<Quote > vec1;
vec1.push_back(Bulk_quote("高数",20,8,0.5));//只是把其中Quote的部分拷贝给vec1了
vec1.push_back(Bulk_quote("高数",20,5,0.5));
double sum1=0.0;
for(auto x:vec1){
sum1+=print_total(std::cout,x,7);
}
std::cout<<"total_price:"<<sum1<<std::endl;
std::vector<std::shared_ptr<Quote> > vec2;
vec2.push_back(std::make_shared<Bulk_quote>("高数",20,8,0.5)); //指针动态绑定
vec2.push_back(std::make_shared<Bulk_quote>("高数",20,5,0.5));
double sum2=0.0;
for(auto x:vec2){
sum2+=print_total(std::cout,*x,7);
}
std::cout<<"total_price:"<<sum2<<std::endl;
return 0;
}
15.8.1节练习：
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