Use map map of the C ++ STL
map is key-value pairs, such as ⼀ ⽐ name corresponding to a Face ⼀ a student number, can define a string string string ⼀ Face human type called "button", student number of type int "value", such as map <string , int> m; course key value may be the amount of other variables will automatically map ~ type automatically to all key-value pairs in accordance with the key zoomed from small to large ⼩ sort, the following method is ⽅ use map often used:
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main() {
map<string, int> m; // 定义⼀一个空的map m，键是string类型的，值是int类型的
m["hello"] = 2; // 将key为"hello", value为2的键值对(key-value)存⼊入map中
cout << m["hello"] << endl; // 访问map中key为"hello"的value, 如果key不不存在，则返回0
cout << m["world"] << endl;
m["world"] = 3; // 将"world"键对应的值修改为3
m[","] = 1; // 设⽴立⼀一组键值对，键为"," 值为1
// ⽤用迭代器器遍历，输出map中所有的元素，键⽤用it->first获取，值⽤用it->second获取
for (auto it = m.begin(); it != m.end(); it++) {
cout << it->first << " " << it->second << endl;
}
// 访问map的第⼀一个元素，输出它的键和值
cout << m.begin()->first << " " << m.begin()->second << endl;
// 访问map的最后⼀一个元素，输出它的键和值
cout << m.rbegin()->first << " " << m.rbegin()->second << endl;
// 输出map的元素个数
cout << m.size() << endl;
return 0;
}
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