2526.txt

北大ACM题目例程 详细的解答过程 程序实现 算法分析

#include "stdio.h"
#include "algorithm"
using namespace std;

struct point
{
	int x,y;
}p[10000];

inline bool cmp( point a, point b )
{
	return a.x < b.x || ( a.x == b.x && a.y < b.y );
}

int n;

int main()
{
	int cas,i,xx,yy;
	
	scanf( "%d", &cas );

	while( cas-- )
	{
		scanf( "%d", &n );
		
		for( i=0; i<n; i++ )
		{
			scanf( "%d %d", &p[i].x, &p[i].y );
		}

		sort( p, p+n, cmp );
		
		xx = p[0].x + p[n-1].x;
		yy = p[0].y + p[n-1].y;

		for( i=1; i<=n/2; i++ )
		{
			if( p[i].x + p[n-1-i].x != xx || p[i].y + p[n-1-i].y != yy )
				break;
		}

		if( i <= n/2 )printf( "no\n" );
		else printf( "yes\n" );
	}

	return 0;
}