2035.cpp

这是哈尔滨工业大学acmOJ的源代码

/*  This Code is Submitted by wywcgs for Problem 2035 on 2005-09-30 at 12:34:47 */ 
#include <stdio.h>
#include <stdlib.h>
#define  MAX  10000

typedef struct {
	long x;
	long y;
} Point;

int cmp(const void*, const void*);

int main()
{
	int c, n, i, j, m, haveCenter;
	Point p[MAX];
	long xm, ym;
	
	scanf("%d", &c);
	for(i = 0; i < c; i++) {
		scanf("%d", &n);
		for(j = 0; j < n; j++) {
			scanf("%ld %ld", &p[j].x, &p[j].y);
		}
		qsort(p, n, sizeof(Point), cmp);
		xm = p[n-1].x + p[0].x;
		ym = p[n-1].y + p[0].y;
		m = (n + 1) / 2;
		haveCenter = 1;
		for(j = 1; j < m; j++) {
			if(p[n-1-j].x + p[j].x != xm) {
				haveCenter = 0;
				break;
			} else if(p[n-1-j].y + p[j].y != ym) {
				haveCenter = 0;
				break;
			}
		}
		if(haveCenter) {
			printf("yes\n");
		} else {
			printf("no\n");
		}
	}

	return 0;
}

int cmp(const void *a, const void *b)
{
	Point *p = (Point*)a, *q = (Point*)b;
	
	if(p->x < q->x) {
		return -1;
	} else if(p->x > q->x) {
		return 1;
	} else {
		if(p->y < q->y) {
			return -1;
		} else {
			return 1;
		}
	}
}