第十一章 关联容器

Posted 2020-10-11 GGBeng

11.1

map：存储关键字-值（key-value）对的容器，关键字起到索引的作用，值则表示与索引相关联的数据；关键字是唯一、有序存储的

vector：存储单一类型元素的容器；元素是按添加顺序存储的

 

11.2

list：频繁在任意处插入/删除元素但不要求有随机访问能力时

vector：在尾部插入/删除元素且要求具有随机访问能力时

deque：在首尾插入/删除元素且要求具有随机访问能力时

map：统计每个单词在输入中出现的次数

set：查找集合中是否包含某个数

 

11.3

 1 #include <iostream>
 2 #include <fstream>
 3 #include <iterator>
 4 #include <vector> 
 5 #include <string>
 6 #include <deque>
 7 #include <list> 
 8 #include <forward_list>
 9 #include <stack>
10 #include <queue>
11 #include <algorithm> 
12 #include <functional>
13 #include <map>
14 #include <set> 
15  
16 using namespace std;
17 using namespace std::placeholders;
18 
19 int main()
20 {
21        map<string, int> jzd;
22        string word;
23        while (cin >> word) {
24            ++jzd[word];
25        }
26        for (auto &i : jzd) {
27            cout << i.first << " occurs about " << i.second << (i.second > 1 ? "times.\n" : "time\n"); 
28        }
29     return 0;
30 }

View Code

 

11.4

 1 #include <iostream>
 2 #include <fstream>
 3 #include <iterator>
 4 #include <vector> 
 5 #include <string>
 6 #include <deque>
 7 #include <list> 
 8 #include <forward_list>
 9 #include <stack>
10 #include <queue>
11 #include <algorithm> 
12 #include <functional>
13 #include <map>
14 #include <set> 
15 #include <cctype>
16  
17 using namespace std;
18 using namespace std::placeholders;
19 
20 int main()
21 {
22        map<string, int> jzd;
23        string word;
24        while (cin >> word) {
25            for (auto &i : word)
26             if (i <= ‘Z‘ && i >= ‘A‘)    i = tolower(i);
27         for (auto it = word.begin(); it != word.end(); ++it) {
28             if (ispunct(*it)) {
29                 it = word.erase(it);
30                 --it;
31             }
32         }
33            ++jzd[word];
34        }
35        for (auto &i : jzd) {
36            cout << i.first << " occurs about " << i.second << (i.second > 1 ? "times.\n" : "time\n"); 
37        }
38     return 0;
39 }

View Code 

 

11.5

map：每个元素都是一个关键字-值对，初始化时必须提供关键字类型和值类型

set：每个元素只是一个关键字，没有值，元素类型就是关键字类型

 

11.6

set：元素都是唯一有序的

list：插入/删除元素很方便

 

11.7

 1 #include <iostream>
 2 #include <fstream>
 3 #include <iterator>
 4 #include <vector> 
 5 #include <string>
 6 #include <deque>
 7 #include <list> 
 8 #include <forward_list>
 9 #include <stack>
10 #include <queue>
11 #include <algorithm> 
12 #include <functional>
13 #include <map>
14 #include <set> 
15 #include <cctype>
16  
17 using namespace std;
18 using namespace std::placeholders;
19 
20 int main()
21 {
22        map<string, vector<string>> imap;
23        string name1, name2;
24        while (cin >> name1) {
25            cin >> name2;
26            imap[name1].push_back(name2);
27        }
28        for (auto &i : imap) {
29            for (auto &j : i.second) {
30                cout << i.first << " " << j << endl;
31            }
32            cout << endl;
33        }
34     return 0;
35 }

View Code

 

11.8

 1 #include <iostream>
 2 #include <fstream>
 3 #include <iterator>
 4 #include <vector> 
 5 #include <string>
 6 #include <deque>
 7 #include <list> 
 8 #include <forward_list>
 9 #include <stack>
10 #include <queue>
11 #include <algorithm> 
12 #include <functional>
13 #include <map>
14 #include <set> 
15 #include <cctype>
16  
17 using namespace std;
18 using namespace std::placeholders;
19 
20 void use_set(const vector<string> &vec)
21 {
22     set<string> iset(vec.begin(), vec.end());
23     for (auto &i : iset)    cout << i << " ";
24     cout << endl;
25 }
26 
27 void use_vector(const vector<string> &vec)
28 {
29     vector<string> ivec(vec.begin(), vec.end());
30     //unique必须要先sort过 
31     sort(ivec.begin(), ivec.end());
32     vector<string>::iterator it = unique(ivec.begin(), ivec.end());
33     ivec.erase(it, ivec.end());
34     for (auto &i : ivec)    cout << i << " ";
35     cout << endl;
36 }
37 
38 int main()
39 {
40     vector<string> vec = {"scout", "peanut", "jack", "peanut", "amazon", "jack", "demo"};
41        use_set(vec);
42        use_vector(vec);
43     return 0;
44 }

View Code

 

11.9