codeforces-653

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本文解析了一道关于选择合适尺寸球送给三位朋友的问题。通过排序和去重的方法，检查是否存在符合条件的三个球，使任意两个球的尺寸相差不超过2，并且尺寸各不相同。

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题目链接：点击打开链接

Limak is a little polar bear. He has n balls, the i-th ball has size ti.

Limak wants to give one ball to each of his three friends. Giving gifts isn't easy — there are two rules Limak must obey to make friends happy:

No two friends can get balls of the same size.
No two friends can get balls of sizes that differ by more than 2.

For example, Limak can choose balls with sizes 4, 5 and 3, or balls with sizes 90, 91 and 92. But he can't choose balls with sizes 5, 5and 6 (two friends would get balls of the same size), and he can't choose balls with sizes 30, 31 and 33 (because sizes 30 and 33 differ by more than 2).

Your task is to check whether Limak can choose three balls that satisfy conditions above.

Input

The first line of the input contains one integer n (3 ≤ n ≤ 50) — the number of balls Limak has.

The second line contains n integers t1, t2, ..., tn (1 ≤ ti ≤ 1000) where ti denotes the size of the i-th ball.

Output

Print "YES" (without quotes) if Limak can choose three balls of distinct sizes, such that any two of them differ by no more than 2. Otherwise, print "NO" (without quotes).

        Examples
      
          input
        
4
18 55 16 17

          output
        
YES

          input
        
6
40 41 43 44 44 44

          output
        
NO

          input
        
8
5 972 3 4 1 4 970 971

          output
        
YES

Note

In the first sample, there are 4 balls and Limak is able to choose three of them to satisfy the rules. He must must choose balls with sizes18, 16 and 17.

In the second sample, there is no way to give gifts to three friends without breaking the rules.

In the third sample, there is even more than one way to choose balls:

Choose balls with sizes 3, 4 and 5.
Choose balls with sizes 972, 970, 971.

题意：一个人要送球给他三个朋友，每个朋友的球大小不能一样，而且任意两个朋友的球大小不能超过 2；

傻逼还去重：

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int n;
int a[100];
int main()
{
	while(~scanf("%d",&n))
	{
		for(int i=0;i<n;i++)
			scanf("%d",&a[i]);
		sort(a,a+n);
		bool flag=0;
		int top=unique(a,a+n)-a; // 去重 
		if(top<3)
		{
			puts("NO");
			continue;
		}
		for(int i=1;i<top-1;i++)
		{
			if(a[i]==a[i-1]+1&&a[i+1]==a[i]+1)
			{
				flag=1;
				break;
			}
		}
		if(flag)	puts("YES");
		else	puts("NO");
	}
	return 0;
}

n的范围也太小了吧，三重 for 水

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int n;
int a[100];
int main()
{
	while(~scanf("%d",&n))
	{
		for(int i=0;i<n;i++)
			scanf("%d",&a[i]);
		bool flag=0;
		for(int i=0;i<n;i++)
		{
			for(int j=0;j<n;j++)
			{
				for(int k=0;k<n;k++)
				{
					if(a[i]==a[j]+1&&a[i]==a[k]-1)
						flag=1;
				}
			}
		}
		if(flag)	puts("YES");
		else	puts("NO");
	}
	return 0;
}