478. Generate Random Point in a Circle (Medium)


Given the radius and x-y positions of the center of a circle, write a function randPoint which generates a uniform random point in the circle.


  1. input and output values are in floating-point.
  2. radius and x-y position of the center of the circle is passed into the class constructor.
  3. a point on the circumference of the circle is considered to be in the circle.
  4. randPoint returns a size 2 array containing x-position and y-position of the random point, in that order.

Example 1:

Output: [null,[-0.72939,-0.65505],[-0.78502,-0.28626],[-0.83119,-0.19803]]

Example 2:

Output: [null,[11.52438,-8.33273],[2.46992,-16.21705],[11.13430,-12.42337]]

Explanation of Input Syntax:

The input is two lists: the subroutines called and their arguments. Solution's constructor has three arguments, the radius, x-position of the center, and y-position of the center of the circle. randPoint has no arguments. Arguments are always wrapped with a list, even if there aren't any.




class Solution {

    double r , x , y;
    public Solution(double radius, double x_center, double y_center) {
        r = radius;
        x = x_center;
        y = y_center;

    public double[] randPoint() {
        double len = Math.sqrt(Math.random()) * r;
        double deg = Math.random() * 2 * Math.PI;
        return new double[]{len * Math.cos(deg) + x, len * Math.sin(deg) + y};

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