README.md

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.

Solutions (Rust)

1. Solution

use rand::{thread_rng, Rng};

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

/**
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
impl Solution {
    fn new(radius: f64, x_center: f64, y_center: f64) -> Self {
        Self {
            radius,
            x_center,
            y_center,
        }
    }

    fn rand_point(&self) -> Vec<f64> {
        let mut rng = thread_rng();
        let delta_x = rng.gen_range(-self.radius, self.radius);
        let delta_y = rng.gen_range(-self.radius, self.radius);

        if delta_x.powi(2) + delta_y.powi(2) <= self.radius.powi(2) {
            vec![self.x_center + delta_x, self.y_center + delta_y]
        } else {
            self.rand_point()
        }
    }
}

/**
 * Your Solution object will be instantiated and called as such:
 * let obj = Solution::new(radius, x_center, y_center);
 * let ret_1: Vec<f64> = obj.rand_point();
 */