hdu5365(几何)

题意:

给出n个整数点坐标,问构成正多边形的方法有几种;

思路:

因为整数点能构成的正多边形只有正四边形;

所以四层for判断正四边形就行;

#include 
#include 

int x[25], y[25];
int square(int x){
    return x * x;
}

int dis(int a, int b){
    return square(x[a] - x[b]) + square(y[a] - y[b]);
}

int judge( int a, int b, int c, int d ){
	int dd = dis(a, c);
	if (dis(a, b) * 2 == dd && dis(b, c) * 2 == dd
			&& dis(c, d) * 2 == dd && dis(d, a) * 2 == dd) return 1;
	return 0;
}
int main () {
	int n;
	while (scanf("%d", &n) == 1)  {
		for (int i = 0; i < n; i++) {
			scanf("%d%d", &x[i], &y[i]);
		}
		int ans = 0;
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				if (i == j)
					continue;
				for (int k = 0; k < n; k++) {
					if(i == k || j == k)
						continue;
					for (int l = 0; l < n; l++) {
						if (i == l || j == l || k == l)
							continue;
						if (judge(i, j, k, l))
							ans++;
					}
				}
			}
		}
		printf("%d\n", ans/8);
	}
	return 0;
}