478. Generate Random Point in a Circle

Description

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.

Note:

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.

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.

Constraints

Approach

Links

• GeeksforGeeks

• Leetcode

• ProgramCreek

• YouTube

Examples

Example 1

Input:

["Solution", "randPoint", "randPoint", "randPoint"]

[[1, 0, 0], [], [], []]

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

Example 2

Input:

["Solution", "randPoint", "randPoint", "randPoint"]

[[10, 5, -7.5], [], [], []]

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

Solutions

Solution 1

/**
 * Time complexity : 
 * Space complexity : 
 */

class Solution {
    
    private static final Random random = new Random();
    private double radius;
    private double x_center;
    private double y_center;

    public Solution(double radius, double x_center, double y_center) {
        this.radius = radius;
        this.x_center = x_center;
        this.y_center = y_center;
    }
    
    public double[] randPoint() {
        double r = Math.sqrt(random.nextDouble()) * radius;
        double theta = random.nextDouble() * 2 * Math.PI;
        return new double[]{
            x_center + r * Math.cos(theta),
            y_center + r * Math.sin(theta)
        };
    }
}

/**
 * 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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