Algorithm

Problem Name: 478. Generate Random Point in a Circle

Problem Link: https://leetcode.com/problems/generate-random-point-in-a-circle/
 

Given the radius and the position of the center of a circle, implement the function randPoint which generates a uniform random point inside the circle.

Implement the Solution class:

  • Solution(double radius, double x_center, double y_center) initializes the object with the radius of the circle radius and the position of the center (x_center, y_center).
  • randPoint() returns a random point inside the circle. A point on the circumference of the circle is considered to be in the circle. The answer is returned as an array [x, y].

 

Example 1:

Input
["Solution", "randPoint", "randPoint", "randPoint"]
[[1.0, 0.0, 0.0], [], [], []]
Output
[null, [-0.02493, -0.38077], [0.82314, 0.38945], [0.36572, 0.17248]]

Explanation
Solution solution = new Solution(1.0, 0.0, 0.0);
solution.randPoint(); // return [-0.02493, -0.38077]
solution.randPoint(); // return [0.82314, 0.38945]
solution.randPoint(); // return [0.36572, 0.17248]

 

Constraints:

  • 0 < radius <= 108
  • -107 <= x_center, y_center <= 107
  • At most 3 * 104 calls will be made to randPoint.

Code Examples

#1 Code Example with Javascript Programming

Code - Javascript Programming


const Solution = function(radius, x_center, y_center) {
  this.radius = radius
  this.x_center = x_center
  this.y_center = y_center
}

Solution.prototype.randPoint = function() {
  let len = Math.sqrt(Math.random()) * this.radius
  let deg = Math.random() * 2 * Math.PI
  let x = this.x_center + len * Math.cos(deg)
  let y = this.y_center + len * Math.sin(deg)
  return [x, y]
}
Copy The Code & Try With Live Editor

Input

x
–
+
cmd
["Solution", "randPoint", "randPoint", "randPoint"] [[1.0, 0.0, 0.0], [], [], []]

Output

x
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cmd
[null, [-0.02493, -0.38077], [0.82314, 0.38945], [0.36572, 0.17248]]

#2 Code Example with Python Programming

Code - Python Programming


class Solution:

    def __init__(self, radius, x_center, y_center):
        self.x, self.y, self.r = x_center, y_center, radius

    def randPoint(self):
        r, angle, scale = random.uniform(0, self.r), random.uniform(0, 2 * math.pi), math.sqrt(random.uniform(0, 1))
        return [self.x + self.r * scale * math.cos(angle), self.y + self.r * scale * math.sin(angle)]
Copy The Code & Try With Live Editor

Input

x
–
+
cmd
["Solution", "randPoint", "randPoint", "randPoint"] [[1.0, 0.0, 0.0], [], [], []]

Output

x
–
+
cmd
[null, [-0.02493, -0.38077], [0.82314, 0.38945], [0.36572, 0.17248]]
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