map容器

简介:

1.1 是关联式容器，自身是有规则，会进行排序，默认排序升序

1.2 数据结构是二叉树，迭代器是双向

1.3 里面的元素是对组，以键值来排序，实值是可以改变

1.4 map容器键值不允许相同

1.5 以[]的方式插入数据时，需要注意会改变value值

例子:

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<map>
#include<string>
using namespace std;

void printMap(map<int, string> &mymap)
{
    for (map<int, string>::iterator it = mymap.begin(); it != mymap.end(); ++it)
    {
        cout << "key:" << it->first << " value:" << it->second << endl;
    }
}

void test01()
{
    map<int, string> mymap;

    //1.第一种插入数据
    mymap.insert(pair<int, string>(3, "aaa"));

    //2.第二种插入数据
    mymap.insert(make_pair(6, "ddd"));

    //3.第三种插入数据
    mymap.insert(map<int, string>::value_type(2, "bbb"));

    //4.第三种插入数据
    mymap[4] = "ccc";

    printMap(mymap);

    cout << mymap.size() << endl;
    mymap[4] = "666";
    cout << mymap[4] << endl;

    cout << mymap.size() << endl;

    //map容器是以键值为主，必须要有键值

}
/*
find(key);//查找键key是否存在,若存在，返回该键的元素的迭代器；/若不存在，返回map.end();
count(keyElem);//返回容器中key为keyElem的对组个数。对map来说，要么是0，要么是1。对multimap来说，值可能大于1。
lower_bound(keyElem);//返回第一个key>=keyElem元素的迭代器。
upper_bound(keyElem);//返回第一个key>keyElem元素的迭代器。
equal_range(keyElem);//返回容器中key与keyElem相等的上下限的两个迭代器。
*/
void test02()
{
    map<int, string> mymap;
    mymap[1] = "aaa1";
    mymap[2] = "aaa2";
    mymap[3] = "aaa3";
    mymap[4] = "aaa4";
    mymap[5] = "aaa5";
    map<int, string>::iterator it = mymap.find(30);
    if (it == mymap.end())
    {
        cout << "查找失败" << endl;
    }
    else
    {
        cout << "查找成功" << endl;
        cout << it->first << " " << it->second << endl;
    }

    multimap<int, string> mumap;
    mumap.insert(make_pair(1, "aa"));
    mumap.insert(make_pair(2, "aa"));
    mumap.insert(make_pair(2, "aa"));
    mumap.insert(make_pair(2, "aa"));
    mumap.insert(make_pair(1, "aa"));

    cout << mumap.count(2) << endl;

    it = mymap.lower_bound(8);
    if (it == mymap.end())
    {
        cout << "查找失败" << endl;
    }
    else
    {
        cout << "查找成功" << endl;
        cout << it->first << " " << it->second << endl;
    }

    it = mymap.upper_bound(3);
    if (it == mymap.end())
    {
        cout << "查找失败" << endl;
    }
    else
    {
        cout << "查找成功" << endl;
        cout << it->first << " " << it->second << endl;
    }
    cout << "-------------------" << endl;
    //返回两个元素的迭代器，元素的对组
    pair<map<int, string>::iterator, map<int, string>::iterator> ret = mymap.equal_range(3);
    if (ret.first != mymap.end())
    {
        cout << "key:" << ret.first->first << " value:" << ret.first->second << endl;
    }
    if (ret.second != mymap.end())
    {
        cout << "key:" << ret.second->first << " value:" << ret.second->second << endl;
    }
}

int main()
{
    test02();
    system("pause");
    return EXIT_SUCCESS;
}