CodeForces 637B Chat Order

最新推荐文章于 2024-03-06 21:32:15 发布

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最新推荐文章于 2024-03-06 21:32:15 发布

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本文介绍了一个简单的算法，用于模拟社交网络中聊天列表的管理。当发送消息给某位朋友时，该聊天会升至列表顶部；若为新聊天，则插入到顶部。通过使用C++实现，并借助map来标记已处理的聊天记录，确保每个聊天只被输出一次。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

思路：水题..其实就是把输入的字符串倒着输出就行了，加个map判重就可以了

#include <cstdio>
#include <queue>
#include <cstring>
#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <map>
#include <string>
#include <set>
#include <ctime>
#include <cmath>
#include <cctype>
using namespace std;
#define maxn 200005
#define LL long long
int cas=1,T;
map<string,int> visit;
string s[maxn];
int main()
{
	int n;
	while (scanf("%d",&n)!=EOF)
	{
		for (int i = 0;i<n;i++)
		{
			cin >> s[i];
	        //visit[s[i]]=1;		
		}
		for (int i = n-1;i>=0;i--)
		{
			if (!visit[s[i]])
				cout << s[i] << endl;
			visit[s[i]]=1;
		}
	}
	//freopen("in","r",stdin);
	//scanf("%d",&T);
	//printf("time=%.3lf",(double)clock()/CLOCKS_PER_SEC);
	return 0;
}

Description

Polycarp is a big lover of killing time in social networks. A page with a chatlist in his favourite network is made so that when a message is sent to some friend, his friend's chat rises to the very top of the page. The relative order of the other chats doesn't change. If there was no chat with this friend before, then a new chat is simply inserted to the top of the list.

Assuming that the chat list is initially empty, given the sequence of Polycaprus' messages make a list of chats after all of his messages are processed. Assume that no friend wrote any message to Polycarpus.

Input

The first line contains integer n (1 ≤ n ≤ 200 000) — the number of Polycarpus' messages. Next n lines enlist the message recipients in the order in which the messages were sent. The name of each participant is a non-empty sequence of lowercase English letters of length at most 10.

Output

Print all the recipients to who Polycarp talked to in the order of chats with them, from top to bottom.

Sample Input

Input

4
alex
ivan
roman
ivan

Output

ivan
roman
alex

Input

8
alina
maria
ekaterina
darya
darya
ekaterina
maria
alina

Output

alina
maria
ekaterina
darya