Leetcode478 随机圆中点

两个问题：

1.随机取半径和角度并不是真正的随机

2.期望的计算

 

 

class Solution {
public:
    Solution(double radius, double x_center, double y_center) {
        rad = radius;
        x = x_center;
        y = y_center;
    }
    
    vector<double> randPoint() {
        const double PI = 3.141592653;
        //rad代表半径 2*PI代表360度==2PI 故对角度和长度都取随机值，并通过开根号的方式控制远离圆心的概率增加，来达到整体的均衡【原本是靠近圆心的点少，所以最后分布会更接近圆心】
        double nr = sqrt(rand() / double(RAND_MAX)) * rad;
        double alpha = rand() / double(RAND_MAX) * 2 * PI;
        double nx = x + nr * cos(alpha);
        double ny = y + nr * sin(alpha);
        return {nx, ny};
    }
private:
    double rad;
    double x, y;
};

/**
 * Your Solution object will be instantiated and called as such:
 * Solution obj = new Solution(radius, x_center, y_center);
 * vector<double> param_1 = obj.randPoint();
 */