map的常用函数find(),size() printf(“%d“,mp.size())

#include<iostream>
#include<map>
using namespace std;
int main()
{
    
    
map<char,int> mp;
mp['a']=20;
mp['b']=30;
mp['c']=40;
printf("%d",mp.size());
map<char,int>::iterator it=mp.find('b');
printf("%c %d\n",it->first,it->second);
}