小结STL之std::list

Posted 2021-12-01 zhanghengyu

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list是C++标准模版库(STL,Standard Template Library)中的部分内容。实际上,list容器就是一个双向链表,可以高效地进行插入删除元素。

使用list容器之前必须加上STL的list容器的头文件：#include<list>

list属于stl所以使用前要加 using std::list; （或者直接全局：using namespace std;）

Member functions

(constructor)Construct list (public member function )//constructor

(destructor)List destructor (public member function )//destructior

operator=Assign content (public member function )//赋值运算符

Iterators:

beginReturn iterator to beginning (public member function )//第一个元素的迭代器，正序

endReturn iterator to end (public member function )//最后一个元素的迭代器在，正序

rbeginReturn reverse iterator to reverse beginning (public member function )//最后一个元素的迭代器，倒序

rendReturn reverse iterator to reverse end (public member function )//第一个元素的迭代器，倒序

cbegin Return const_iterator to beginning (public member function )

cend Return const_iterator to end (public member function )

crbegin Return const_reverse_iterator to reverse beginning (public member function )

crend Return const_reverse_iterator to reverse end (public member function )

Capacity:

emptyTest whether container is empty (public member function )//返回是否为空

sizeReturn size (public member function )//返回当前大小

max_sizeReturn maximum size (public member function )//返回最大大小

Element access:

frontAccess first element (public member function )//返回第一个元素

backAccess last element (public member function )//返回最后一个元素

Modifiers:

assignAssign new content to container (public member function )

emplace_front Construct and insert element at beginning (public member function )

push_frontInsert element at beginning (public member function )

pop_frontDelete first element (public member function )

emplace_back Construct and insert element at the end (public member function )

push_backAdd element at the end (public member function )

pop_backDelete last element (public member function )

emplace Construct and insert element (public member function )//构造并插入

insertInsert elements (public member function )//向list中插入某个元素

eraseErase elements (public member function )//删除某个元素

swapSwap content (public member function )//交换一个列表的两个元素

resizeChange size (public member function )//重新设定大小

clearClear content (public member function )//清空

Operations:

spliceTransfer elements from list to list (public member function )//移动（从一个list到另一个list）

removeRemove elements with specific value (public member function )//去除特定值的元素

remove_ifRemove elements fulfilling condition (public member function template )//去除符合条件的元素

uniqueRemove duplicate values (public member function )//去除重复元素

mergeMerge sorted lists (public member function )//合并

sortSort elements in container (public member function )//排序

reverseReverse the order of elements (public member function )//反转

Observers:

get_allocatorGet allocator (public member function )

Non-member function overloads

relational operators (list) Relational operators for list (function )

swap (list) Exchanges the contents of two lists (function template ) //交换两个列表

下面对几个常用的操作举例：

1.构建及初始化

// 创建实例以及赋值
#include <iostream>
#include <list>
using namespace std;
int main () {
    //第一种，通过构造函数
    int myints[] = {75,23,65,42,13};
    list<int> mylist1(myints, myints+5);
    list<int> mylist2(2,100);         // 2个值为100的元素
    //第二种，用push_back，或push_front
    for (int i = 1; i <= 5; ++i) mylist1.push_back(i);
    mylist2.push_front (200);
    mylist2.push_front (300);
    //第三种,用assign
    list<int> first;
    list<int> second;
    first.assign(7,100);                       // 给first添加7个值为100的元素
    second.assign(first.begin(), first.end()); // 复制first给second
    int myints[] = {16, 8, 4};
    first.assign (myints, myints + 3);         // 将数组myints的内容添加给first

    //第四种，见insert函数
    return 0;
}

2.迭代器的创建及使用迭代器遍历

//list的遍历
#include <iostream>
#include <list>
using namespace std;
int main () {
    int myints[] = {75,23,65,42,13};
    list<int> mylist (myints,myints+5);
    cout << "mylist contains:";
    //这是正序输出：
    for (list<int>::iterator it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;
    //使用c++11和c++14的新特性auto更加方便准确
    auto it = mylist.begin();

    list.clear();
    //逆序输出：
    for (int i = 1; i <= 5; ++i) mylist.push_back(i);
    cout << "mylist backwards:";
    for (list<int>::reverse_iterator rit = mylist.rbegin(); rit != mylist.rend(); ++rit)
        cout << ‘ ‘ << *rit;
    cout << ‘\n‘;
    return 0;
}
    
输出结果为：
mylist contains: 75 23 65 42 13
mylist backwards: 5 4 3 2 1

3.获取列表信息

// list::assign
#include <iostream>
#include <list>
using namespace std;
int main () {
    list<int> first;
    list<int> second;
    first.assign(7,100);                      // 给first添加7个值为100的元素
    second.assign(first.begin(), first.end()); // 复制first给second

    int myints[] = {16, 8, 4};
    first.assign (myints, myints + 3);            // 将数组myints的内容添加给first

    cout << "Size of first: " << int (first.size()) << ‘\n‘;
    cout << "Size of second: " << int (second.size()) << ‘\n‘;
    return 0;
}
输出结果为：
Size of first: 3
Size of second: 7

　　2.push和pop添加元素

　　　　因为list是双向的所有总共有push_front ,push_back ,pop_front,po_back四种

#include <iostream>
#include <list>
using namespace std;
int main () {
    list<int> mylist (2,100);         // 2个值为100的元素
    // list::push_front
    mylist.push_front (200);
    mylist.push_front (300);

    cout << "mylist contains:";
    for (list<int>::iterator it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

    // list::pop_front
    cout << "Popping out the elements in mylist:";
    while (!mylist.empty()) {
        cout << ‘ ‘ << mylist.front();
        mylist.pop_front();
    }
    cout << "\nFinal size of mylist is " << mylist.size() << ‘\n‘;

    // list::push_back
    int myint;
    cout << "Please enter some integers (enter 0 to end):\n";
    do {
        cin >> myint;
        mylist.push_back (myint);
    } while (myint);
    cout << "mylist contains:";
    for (list<int>::iterator it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

    // list::pop_back
    while (!mylist.empty()) {
        cout << ‘ ‘ <<  mylist.back();
        mylist.pop_back();
    }
    cout << "\nFinal size of mylist is " << mylist.size() << ‘\n‘;

    return 0;
}
输出结果：
mylist contai: 300 200 100 100
Popping out the elements in mylist: 300 200 100 100
Final size of mylist is 0
Please enter some integers (enter 0 to end):
23 8 5 6 0
mylist contains: 56 23 8 5 6 0
6 5 8 23 56
Final size of mylist is 0

　　3.insert插入新元素

// inserting into a list
#include <iostream>
#include <list>
#include <vector>
using namespace std;
int main () {
    list<int> mylist;
    list<int>::iterator it;
    // 初始化
    for (int i = 1; i <= 5; ++i) mylist.push_back(i); // 1 2 3 4 5
    it = mylist.begin();
    ++it;       // 迭代器it现在指向数字2                      ^
    //在i0t指向的位置出插入元素10
    mylist.insert (it,10);                        // 1 10 2 3 4 5

    // "it" 仍然指向数字2                                   ^
    //在it指向的位置出插入两个元素20
    mylist.insert (it,2,20);                      // 1 10 20 20 2 3 4 5

    --it;       // 现在it指向数字20                             ^

    vector<int> myvector (2,30); //创建vector容器，并初始化为含有2个值为30的元素
    //将vector容器的值插入list中
    mylist.insert (it,myvector.begin(),myvector.end());
                                                // 1 10 20 30 30 20 2 3 4 5
    //it仍然指向数字20                            //               ^
    cout << "mylist contains:";
    for (it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

    return 0;
}
输出结果：
mylist contains: 1 10 20 30 30 20 2 3 4 5

　　4.erases删除元素

// erasing from list
#include <iostream>
#include <list>
using namespace std;
int main () {
    list<int> mylist;
    list<int>::iterator it1,it2;

    // set some values:
    for (int i = 1; i < 10; ++i) mylist.push_back(i*10);

                                // 10 20 30 40 50 60 70 80 90
    it1 = it2 = mylist.begin(); // ^^
    advance (it2,6);            // ^                 ^
    ++it1;                      //    ^              ^

    it1 = mylist.erase (it1);   // 10 30 40 50 60 70 80 90
                                //    ^           ^


    it2 = mylist.erase (it2);   // 10 30 40 50 60 80 90
                                //    ^           ^

    ++it1;                      //       ^        ^
    --it2;                      //       ^     ^
    //没有变量接收其返回值
    mylist.erase (it1,it2);     // 10 30 60 80 90
                                //       ^
    cout << "*it1 : " << *it1 << endl;
    cout << "mylist contains:";
    for (it1 = mylist.begin(); it1 != mylist.end(); ++it1)
        cout << ‘ ‘ << *it1;
    cout << ‘\n‘;

  return 0;
}
输出结果：
it1 : 40
mylist contains: 10 30 60 80 90

　　5.clear（）清空

5.对列表的一些操作

　　1.unique 删除重复值

// list::unique
#include <iostream>
#include <cmath>
#include <list>
using namespace std;
// a binary predicate implemented as a function:
bool same_integral_part (double first, double second) { return ( int(first)==int(second) ); }

// a binary predicate implemented as a class:
struct is_near {
    bool operator() (double first, double second) { return (fabs(first-second)<5.0); }
};

int main () {
    double mydoubles[] = { 12.15, 2.72, 73.0, 12.77, 3.14,
                       12.77, 73.35, 72.25, 15.3, 72.25 };
    list<double> mylist (mydoubles,mydoubles+10);
    cout << "mylist contains:";
    for (list<double>::iterator it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;
    
    mylist.unique();
    cout << "mylist contains:";
    for (list<double>::iterator it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

    mylist.sort();             //  2.72,  3.14, 12.15, 12.77, 12.77,
                             // 15.3,  72.25, 72.25, 73.0,  73.35

    mylist.unique();           //  2.72,  3.14, 12.15, 12.77
                             // 15.3,  72.25, 73.0,  73.35
    cout << "mylist contains:";
    for (list<double>::iterator it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

    mylist.unique (same_integral_part);  //  2.72,  3.14, 12.15
                                       // 15.3,  72.25, 73.0
    cout << "mylist contains:";
    for (list<double>::iterator it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

    mylist.unique (is_near());           //  2.72, 12.15, 72.25

    cout << "mylist contains:";
    for (list<double>::iterator it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

  return 0;
}
输出结果：
mylist contains: 12.15 2.72 73 12.77 3.14 12.77 73.35 72.25 15.3 72.25
mylist contains: 12.15 2.72 73 12.77 3.14 12.77 73.35 72.25 15.3 72.25
mylist contains: 2.72 3.14 12.15 12.77 15.3 72.25 73 73.35
mylist contains: 2.72 3.14 12.15 15.3 72.25 73
mylist contains: 2.72 12.15 72.25

　　2.sort 排序

　　　　void sort();//默认升序

　　　　void sort(bool cmp);//按照自定的cmp函数的true值排列

　　　　对于自定的类型还可以在共有函数中重载“<”运算符进行定义

// list::sort
#include <iostream>
#include <list>
#include <string>
#include <cctype>
using namespace std;
// comparison, not case sensitive.
bool compare_nocase (const string& first, const string& second) {
    unsigned int i = 0;
    while ((i < first.length()) && (i < second.length()) ) {
        //将大写字母转为小写字母
        if (tolower(first[i]) < tolower(second[i])) return true;
        else if (tolower(first[i]) > tolower(second[i])) return false;
        ++i;
    }
    return ( first.length() < second.length() );
}

int main () {
    list<string> mylist;
    list<string>::iterator it;
    mylist.push_back ("one");
    mylist.push_back ("two");
    mylist.push_back ("Three");

    mylist.sort();

    cout << "mylist contains:";
    for (it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

    mylist.sort(compare_nocase);

    cout << "mylist contains:";
    for (it = mylist.begin(); it != mylist.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

  return 0;
}
输出结果：
mylist contains: Three one two
mylist contains: one Three two

　　3.merge 合并两个有序列表

　　　　注意：一定是有序才可以，不然在合并前要先sort（）

// list::merge
#include <iostream>
#include <list>
using namespace std;
// compare only integral part:
bool mycomparison (double first, double second) { return ( (first)<(second) ); }

int main () {
    list<double> first, second;

    first.push_back (3.1);
    first.push_back (2.2);
    first.push_back (2.9);

    second.push_back (3.7);
    second.push_back (7.1);
    second.push_back (1.4);

    first.sort();
    second.sort();

    first.merge(second);
    cout << "first contains:";
    for (list<double>::iterator it = first.begin(); it != first.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;
    // (second 现在为空)

    second.push_back (2.1);
    second.push_back(2.5);

    first.merge(second,mycomparison);
    cout << "first contains:";
    for (list<double>::iterator it = first.begin(); it != first.end(); ++it)
        cout << ‘ ‘ << *it;
    cout << ‘\n‘;

  return 0;
}
输出结果：
first contains: 1.4 2.2 2.9 3.1 3.7 7.1
first contains: 1.4 2.1 2.2 2.5 2.9 3.1 3.7 7.1

Member functions

(constructor): Construct list (public member function )

(destructor): List destructor (public member function )

operator=: Assign content (public member function )

Iterators:

begin: Return iterator to beginning (public member function )

end: Return iterator to end (public member function )

rbegin: Return reverse iterator to reverse beginning (public member function )

rend: Return reverse iterator to reverse end (public member function )

cbegin: Return const_iterator to beginning (public member function )

cend: Return const_iterator to end (public member function )

crbegin: Return const_reverse_iterator to reverse beginning (public member function )

crend: Return const_reverse_iterator to reverse end (public member function )

Capacity:

empty: Test whether container is empty (public member function )

size: Return size (public member function )

max_size: Return maximum size (public member function )

Element access:

front: Access first element (public member function )

back: Access last element (public member function )

Modifiers:

assign: Assign new content to container (public member function )

emplace_front: Construct and insert element at beginning (public member function )

push_front: Insert element at beginning (public member function )

pop_front: Delete first element (public member function )

emplace_back: Construct and insert element at the end (public member function )

push_back: Add element at the end (public member function )

pop_back: Delete last element (public member function )

emplace: Construct and insert element (public member function )

insert: Insert elements (public member function )

erase: Erase elements (public member function )

swap: Swap content (public member function )

resize: Change size (public member function )

clear: Clear content (public member function )

Operations:

splice: Transfer elements from list to list (public member function )

remove: Remove elements with specific value (public member function )

remove_if: Remove elements fulfilling condition (public member function template )

unique: Remove duplicate values (public member function )

merge: Merge sorted lists (public member function )

sort: Sort elements in container (public member function )

reverse: Reverse the order of elements (public member function )

Observers:

get_allocator: Get allocator (public member function )

Non-member function overloads

relational operators (list): Relational operators for list (function )

swap (list): Exchanges the contents of two lists (function template )

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