袁老师版题解

#include<bits/stdc++.h>
using namespace std;

int main()
{

int n;
cin >> n;

string d,f;//d=操作，f=指纹;
vector <string> v; //向量容器，类型为string,名为v 
while(n--)
{
	cin >> d;
	if(d=="ADD")
	{
		cin >> f;
		//查找find(容器开始内存，结束内存地址,要找的东西) 
		if(1==1)
		{
			v.push_back(f);//向最后推一个f变量 
			cout << "success\n";
		}
		else
		{
			cout << "already exists\n";
		}			
	}
	 
	if(d=="DEL")
	{
		cin >> f;
		if( find(v.begin(), v.end(), f) == v.end())
		{
			cout << "non-existent\n";
		}
		else{
			//删除 找到的送代器对象
			v.erase( find(v.begin(), v.end(), f)  );
			cout << "success\n"; 
		}
	}
	
	if(d=="VIEW")
	{
		if(v.size()==0)
			cout << "empty\n";
		else{
			for(int i=0; i<v.size(); i++)
				cout << i+1 << ". " << v[i] << endl;
		}	
	}
	 
	if(d=="UNLOCK")
	{
		cin >> f;
		if( find(v.begin(), v.end(), f) == v.end() )
			cout << "NO\n";
		else
			cout << " Yes\n";		
	} 
}
return 0;

}