HDU - 4709 Herding

 1
4
-1.00 0.00
0.00 -3.00
2.00 0.00
2.00 2.00 

 2.00 

Source

思路： 枚举计算

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
const int MAXN = 150;
const double INF = 100000000.0;

struct node {
	double x, y;
} point[MAXN];
int n;

double dis(int a, int b) {
	return sqrt((point[a].x-point[b].x)*(point[a].x-point[b].x)+(point[a].y-point[b].y)*(point[a].y-point[b].y));
}

double cal(int a, int b, int c) {
	double A = dis(a, b);
	double B = dis(a, c);
	double C = dis(b, c);
	double p = (A+B+C)/2;
	return sqrt(p*(p-A)*(p-B)*(p-C));
}

int main() {
	int t;
	scanf("%d", &t);
	while (t--) {
		scanf("%d", &n);
		for (int i = 0; i < n; i++)
			scanf("%lf%lf", &point[i].x, &point[i].y);
		double ans = 1e20;
		int flag = 0;
		for (int i = 0; i < n; i++)
			for (int j = i+1; j < n; j++)
				for (int k = j+1; k < n; k++) {
					double tmp = cal(i, j, k);
					if (fabs(tmp) >= 0.01) {
						flag = 1;
						ans = min(ans, tmp);
					}
				}
		if (!flag) 
			printf("Impossible\n");
		else printf("%.2lf\n", ans);
	}
}