nyoj-1099-Lan Xiang's Square（几何，水题）

题目链接

 /*
     Name:nyoj-1099-Lan Xiang's Square
     Copyright:
     Author:
     Date: 2018/4/26 9:19:19
     Description:
     给4个点，判断是否形成正方形
     double类型的值比较大小，直接判断==0竟然A了，然而小于1e-6竟然WA
 */
 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 using namespace std;
 struct node {
     double x, y;
 }nodes[];
 double length_edge(node a, node b) {
     return (b.x - a.x)*(b.x - a.x) + (b.y - a.y)*(b.y - a.y);
 }
 int main()
 {
 //    freopen("in.txt", "r", stdin);
     int t;
     cin>>t;
     while (t--) {
         for (int i=; i<; i++)
             cin>>nodes[i].x>>nodes[i].y;
         double edge[];
         edge[] = length_edge(nodes[], nodes[]);
         edge[] = length_edge(nodes[], nodes[]);
         edge[] = length_edge(nodes[], nodes[]);
         if (count(edge, edge+, ) >) {
             cout<<"No"<<endl;
             continue;
         }
         sort(edge, edge+);
 //        if (edge[0] - edge[2] + edge[1] < 1e-6 && (edge[0] - edge[1]) < 1e-6) { //WA
         if (edge[] - edge[] + edge[] ==  && (edge[] - edge[])  == ) {
             cout<<"Yes"<<endl;
         } else {
             cout<<"No"<<endl;
         }
     }
     return ;
 }