384. Shuffle an Array

Given an integer array nums, design an algorithm to randomly shuffle the array.

Implement the Solution class:

  • Solution(int[] nums) Initializes the object with the integer array nums.
  • int[] reset() Resets the array to its original configuration and returns it.
  • int[] shuffle() Returns a random shuffling of the array.

 

Example 1:

Input
["Solution", "shuffle", "reset", "shuffle"]
[[[1, 2, 3]], [], [], []]
Output
[null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]

Explanation
Solution solution = new Solution([1, 2, 3]);
solution.shuffle();    // Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must be equally likely to be returned. Example: return [3, 1, 2]
solution.reset();      // Resets the array back to its original configuration [1,2,3]. Return [1, 2, 3]
solution.shuffle();    // Returns the random shuffling of array [1,2,3]. Example: return [1, 3, 2]

 

Constraints:

  • 1 <= nums.length <= 200
  • -106 <= nums[i] <= 106
  • All the elements of nums are unique.
  • At most 5 * 104 calls will be made to reset and shuffle.

Rust Solution

use rand::prelude::*;

struct Solution {
    rng: ThreadRng,
    nums: Vec<i32>,
    n: usize,
}

impl Solution {
    fn new(nums: Vec<i32>) -> Self {
        let n = nums.len();
        let rng = thread_rng();
        Solution { rng, nums, n }
    }

    fn reset(&self) -> Vec<i32> {
        self.nums.to_vec()
    }

    fn shuffle(&mut self) -> Vec<i32> {
        let mut v = self.nums.to_vec();
        let n = self.n;
        for i in 0..n {
            let j = self.rng.gen_range(i, n);
            v.swap(i, j);
        }
        v
    }
}

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