HDU 1700 Points on Cycle （几何 向量旋转）

 1 #include<cmath>
 2 #include<cstdio>
 3 #include<algorithm>
 4 using namespace std;
 5 
 6 const double PI = acos(-1.0);
 7 
 8 struct Point{
 9     double x, y;
10 
11     Point(double x = 0, double y = 0): x(x), y(y){}
12 
13     void scan(){
14         scanf("%lf%lf", &x, &y);
15     }
16 
17     void print(){
18         printf("%.3lf %.3lf", x, y);
19     }
20 
21     bool operator < (const Point &other){
22         return y < other.y || (y == other.y && x < other.x);
23     }
24 };
25 
26 typedef Point Vector;
27 
28 Vector rotate(Vector A, double rad){//向量旋转公式
29     return Vector(A.x * cos(rad) - A.y * sin(rad), A.y * cos(rad) + A.x * sin(rad));
30 }
31 
32 int main(){
33     int t;
34     Point p[3];
35     scanf("%d", &t);
36     while(t--){
37         p[0].scan();
38 
39         p[1] = rotate(p[0], PI * 2 / 3);//逆时针旋转120度
40         p[2] = rotate(p[0], -PI * 2 / 3);//顺时针旋转120度
41 
42         if(p[2] < p[1]) swap(p[1], p[2]);//按题目要求输出
43 
44         p[1].print(); putchar(‘ ‘);
45         p[2].print(); putchar(‘\n‘);
46     }
47     return 0;
48 }