rt，明明删了，输出时元素个数还是1........

#include <iostream>
#include <map>
using namespace std;
map <string,int> a;
int main()
{
	int Q;cin>>Q;
	//初始化
	while(Q--)
	{
		int x;cin>>x;
		if(x==1)
		{
			string name; int score;cin>>name>>score;
			a[name]=score;
			cout<<"OK"<<endl;
			continue;
		}
		//插入与修改
		if(x==2)
		{
			string name;cin>>name;
			if(a[name]) cout<<a[name]<<endl;
			else cout<<"Not found"<<endl;
			continue;
		}
		//查询
		if(x==3)
		{
			string name;cin>>name;
			if(a[name]) 
			{
				a.erase(name);
				cout<<"Deleted successfully"<<endl;
//				cout<<a.size()<<endl;
				//这是输出的是0，但到操作4时又变成1了QwQ
			}
			else cout<<"Not found"<<endl;
			continue;
		}
		//删除
		if(x==4) 
		{ 
			cout<<a.size()<<endl;
		}
		//汇总
	}
	//处理 
	return 0;
}
/*
in:
5
1 lxl 10
2 lxl
3 lxl
2 lxl
4
out:
OK
10
Deleted successfully
Not found
0
*/

这段代码样例的输出：

OK
10
Deleted successfully
Not found
1