ACM——Points on Cycle

#include<cmath>
#include<cstdio>
#include<algorithm>//交换函数

using namespace std;

const double PI = acos(-1.0);//就是pi的值

struct Point
{
    double x, y;

    Point(double x = 0, double y = 0): x(x), y(y){}

    void scan()
    {
        scanf("%lf%lf", &x, &y);
    }

    void print()
    {
        printf("%.3lf %.3lf", x, y);
    }

};



Point rotate(Point A, double rad)
{
    return Point(A.x * cos(rad) - A.y * sin(rad), A.y * cos(rad) + A.x * sin(rad));//旋转向量公式
}

int main()
{
    int i;
    Point p[3];
    scanf("%d", &i);
    while(i--)
    {
        p[0].scan();
        p[1] = rotate(p[0], PI * 2 / 3);//逆时针旋转120度
        p[2] = rotate(p[0], -PI * 2 / 3);//顺时针旋转120度

        if(p[2].y < p[1].y||(p[2].y == p[1].y && p[2].x < p[1].x))
            swap(p[1], p[2]);//交换

        p[1].print(); //
        printf(" ");

        p[2].print(); //
        printf("\n");
    }
    return 0;
}