384. Shuffle an Array (Medium)

https://leetcode.com/problems/shuffle-an-array/

Shuffle a set of numbers without duplicates.

Example:

// Init an array with set 1, 2, and 3.
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned.
solution.shuffle();

// Resets the array back to its original configuration [1,2,3].
solution.reset();

// Returns the random shuffling of array [1,2,3].
solution.shuffle();

Solutions

class Solution {

    int[] nums;
    int[] numsCopy;

    public Solution(int[] nums) {
        this.nums = nums;

        numsCopy = new int[nums.length];

        reset();
    }

    public int[] reset() {
        System.arraycopy(nums, 0, numsCopy, 0, nums.length);

        return nums;
    }

    private void swap(int[] nums, int x, int y) {
        int tmp = nums[x];
        nums[x] = nums[y];
        nums[y] = tmp;
    }

    public int[] shuffle() {
        for (int i = numsCopy.length - 1; i >= 0; i--) {
            int randIdx = (int) (Math.random() * (i + 1));

            swap(numsCopy, randIdx, i);
        }

        return numsCopy;
    }
}

Incorrect Solutions

References

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