题目链接
1 /*
2 Name:nyoj-1099-Lan Xiang's Square
3 Copyright:
4 Author:
5 Date: 2018/4/26 9:19:19
6 Description:
7 给4个点，判断是否形成正方形
8 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
9 */
10 #include <iostream>
11 #include <cstdio>
12 #include <algorithm>
13 using namespace std;
14 struct node {
15 double x, y;
16 }nodes[5];
17 double length_edge(node a, node b) {
18 return (b.x - a.x)*(b.x - a.x) + (b.y - a.y)*(b.y - a.y);
19 }
20 int main()
21 {
22 // freopen("in.txt", "r", stdin);
23 int t;
24 cin>>t;
25 while (t--) {
26 for (int i=0; i<4; i++)
27 cin>>nodes[i].x>>nodes[i].y;
28 double edge[4];
29 edge[0] = length_edge(nodes[0], nodes[1]);
30 edge[1] = length_edge(nodes[0], nodes[2]);
31 edge[2] = length_edge(nodes[0], nodes[3]);
32 if (count(edge, edge+3, 0) >0) {
33 cout<<"No"<<endl;
34 continue;
35 }
36 sort(edge, edge+3);
37 // if (edge[0] - edge[2] + edge[1] < 1e-6 && (edge[0] - edge[1]) < 1e-6) { //WA
38 if (edge[0] - edge[2] + edge[1] ==0 && (edge[0] - edge[1]) == 0) {
39 cout<<"Yes"<<endl;
40 } else {
41 cout<<"No"<<endl;
42 }
43 }
44 return 0;
45 }