题意翻译

CF864A Fair Game

题意: Petya和Vasya决定玩一个游戏,他们有偶数张卡片,每张卡片上一个数字.每人选择一个数字(两个人选择的数字不能相同),选择了该数字就意味着需要把写有这个数字的所有卡片都拿走.Petya和Vasya认为,这个游戏是公平的,当仅当两个人可以拿走全部的卡片并且两人拿走的卡片数相同,否则这个游戏就是不公平的.

读入: 第一行:卡片数量n(2<=n<=100),接下来n行每行一个数字表示第i张卡片上的数字

输出: 第一行表示游戏是否公平,公平输出YES,不公平输出NO;若游戏公平,第二行输出两个数字表示Petya和Vasya分别选择的数字

Translated by 凌幽

题目描述

Petya and Vasya decided to play a game. They have nn cards ( nn is an even number). A single integer is written on each card.

Before the game Petya will choose an integer and after that Vasya will choose another integer (different from the number that Petya chose). During the game each player takes all the cards with number he chose. For example, if Petya chose number 55 before the game he will take all cards on which 55 is written and if Vasya chose number 1010before the game he will take all cards on which 1010 is written.

The game is considered fair if Petya and Vasya can take all nn cards, and the number of cards each player gets is the same.

Determine whether Petya and Vasya can choose integer numbers before the game so that the game is fair.

输入输出格式

输入格式：

The first line contains a single integer nn ( 2<=n<=1002<=n<=100 ) — number of cards. It is guaranteed that nn is an even number.

The following nn lines contain a sequence of integers a_{1},a_{2},...,a_{n}a1​,a2​,...,an​ (one integer per line, 1<=a_{i}<=1001<=ai​<=100 ) — numbers written on the nn cards.

输出格式：

If it is impossible for Petya and Vasya to choose numbers in such a way that the game will be fair, print "NO" (without quotes) in the first line. In this case you should not print anything more.

In the other case print "YES" (without quotes) in the first line. In the second line print two distinct integers — number that Petya should choose and the number that Vasya should choose to make the game fair. If there are several solutions, print any of them.

输入输出样例

4

11

27

27

11

YES

11 27

2

6

6

NO

6

10

20

30

20

10

20

NO

6

1

1

2

2

3

3

NO

说明

In the first example the game will be fair if, for example, Petya chooses number 1111 , and Vasya chooses number 2727. Then the will take all cards — Petya will take cards 11 and 44 , and Vasya will take cards 22 and 33 . Thus, each of them will take exactly two cards.

In the second example fair game is impossible because the numbers written on the cards are equal, but the numbers that Petya and Vasya should choose should be distinct.

In the third example it is impossible to take all cards. Petya and Vasya can take at most five cards — for example, Petya can choose number 1010 and Vasya can choose number 2020 . But for the game to be fair it is necessary to take 66 cards.

#include<cstdio>

#include<cstring>

#include<iostream>

#include<algorithm>

#define MAXN 101

using namespace std;

int n,sum,ans;

int num[MAXN],vis[MAXN];

int main(){

    scanf("%d",&n);

    for(int i=;i<=n;i++){

        scanf("%d",&num[i]);

        vis[num[i]]++;

    }

    for(int i=;i<=;i++){

        if(vis[i]){

            sum++;

            if(ans!=&&vis[i]!=ans){ cout<<"NO";return ; }

            ans=vis[i];

            if(sum>){ cout<<"NO";return ; }

        }

    }

    if(sum!=){ cout<<"NO";return ; }

    cout<<"YES"<<endl;

    for(int i=;i<=;i++)

        if(vis[i])    cout<<i<<" ";

}