FZU 2110 Star

题目链接：Star

...计算几何水题，直接暴力判断任意三个点是不是能组成三角形就可以了。

判断是锐角三角形的条件是 a^2+b^2>c^2(c=max(a, b, c)).

坑点在，说好的integer,如果不是double 型，就WA了哦~~~

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <math.h>
#define eps 1e-9
using namespace std;

struct Point{
    int x, y;
}p[210000];

double dis(Point a, Point b) {
    double disx = (a.x-b.x)*(a.x-b.x);
    double disy = (a.y-b.y)*(a.y-b.y);
    double ans = disx + disy;
    return ans;
}


int main() {
    int t;
    cin >> t;
    while(t--) {
        int n;
        cin >> n;
        for (int i=0; i<n; ++i) {
            cin >> p[i].x >> p[i].y;
        }

        int ans = 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 num[3];
                    num[0] = dis(p[i], p[j]);
                    num[1] = dis(p[i], p[k]);
                    num[2] = dis(p[j], p[k]);
                    sort(num, num+3);
                    if (num[0] + num[1] + eps > num[2]) {
                        ans++;
                    }
                }
            }
        }

        cout << ans << endl;
    }
    return 0;
}