C++ map 基本操作

#include<iostream>#include<stdlib.h>#include<string>#include<map>using namespace std;typedef map<string,long long> URL_COUNT;//map的打印void print(URL_COUNT url_count){        for(map<string,long long>::iterator i = url_count.begin(); i!=url_count.end(); i++){                cout << i->first << " " << i->second <<endl;        }} void print_ele(map<string,long long>::iterator ele){        cout << ele->first << "=>" << ele->second << endl;}int main(){        //map的建立        URL_COUNT url_count;        //************************************************************        //map的插入        //map[key] = value        url_count["a"] = 1;        url_count["b"] = 2;        url_count["c"] = 3;        //insert(map<string,long long>::value_type(key,value))        url_count.insert(map<string,long long>::value_type("e",5));        //insert(make_pair(key,value))        url_count.insert(make_pair("f",6));        //insert(pair<string,int> p)        pair<string, int> p;        p.first = "g";        p.second = 7;        url_count.insert(p);        //不正确的插入方式        //url_count.insert("d",4);        print(url_count);        //*************************************************************        //map的查找        //count函数只返回0或者1        cout << url_count.count("e") << endl;        cout << url_count.count("s") << endl;        //find函数返回key对应的对象的迭代器        print_ele(url_count.find("f"));        //没有找到时返回Segmentation fault,慎用        //print_ele(url_count.find("s"));        //*************************************************************        //map的删除        //erase(key)，有则删除返回1，无则返回0        cout << url_count.erase("f") << endl;        //erase(指向map元素的迭代器)        map<string,long long>::iterator i = url_count.find("g");        url_count.erase(i);        print(url_count);        return 0;}

返回结果：

a 1
b 2
c 3
e 5
f 6
g 7
1
0
f=>6
1
a 1
b 2
c 3
e 5