478. Generate Random Point in a Circle

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.

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]]

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.

Rust Solution

use rand::prelude::*;

struct Solution {
    radius: f64,
    x_center: f64,
    y_center: f64,
    rng: ThreadRng,
}

impl Solution {
    fn new(radius: f64, x_center: f64, y_center: f64) -> Self {
        let rng = rand::thread_rng();
        Solution {
            radius,
            x_center,
            y_center,
            rng,
        }
    }

    fn rand_point(&mut self) -> Vec<f64> {
        let mut x = self.rng.gen_range(-self.radius, self.radius);
        let mut y = self.rng.gen_range(-self.radius, self.radius);
        while x * x + y * y > self.radius * self.radius {
            x = self.rng.gen_range(-self.radius, self.radius);
            y = self.rng.gen_range(-self.radius, self.radius);
        }
        vec![x + self.x_center, y + self.y_center]
    }
}

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