pku1859.cpp

这是ACM 方面的资料 是PKU的 北京大学的出来的

#include <stdio.h>
#include <stdlib.h>

typedef struct 
{
	int x, y;
}Point;

Point p[20001], sm;
int N;

int cp(const void *a, const void *b)
{
	Point *aa = (Point *)a;
	Point *bb = (Point *)b;
	if (aa->x != bb->x)
	{
		return aa->x - bb->x;
	}
	return aa->y - bb->y;
}

int OK(int i, int j)
{
	if (p[i].x + p[j].x == sm.x && p[i].y + p[j].y == sm.y)
	{
		return 1;
	}
	return 0;
}

int main()
{
	int i;
	Point tp;
	while (scanf("%d", &N) != EOF && N)
	{
		for (i = 0; i < N; i++)
		{
			scanf("%d%d", &p[i].x, &p[i].y);
		}
		qsort(p, N, sizeof(p[0]), cp);
		sm.x = p[0].x + p[N - 1].x;
		sm.y = p[0].y + p[N - 1].y;
		for (i = N / 2; i >= 0; i--)
		{
			if (OK(i, N - 1 - i) == 0)
			{
				printf("This is a dangerous situation!\n");
				break;
			}
		}
		if (i < 0)
		{
			printf("V.I.P. should stay at (%.1lf,%.1lf).\n", sm.x / 2.0, sm.y / 2.0);
		}
	}
	return 0;
}