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();

Solution

public class Solution {

    int[] nums;
    Random random;

    public Solution(int[] nums) {
        this.nums = nums;
        this.random = new Random();
    }

    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        return nums;
    }

    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
        int[] result = new int[nums.length];
        if (nums.length == 0) {
            return new int[0];
        }

        result[0] = nums[0];

        for (int i = 1; i < nums.length; i++) {
            int swapIndex = random.nextInt(i + 1);
            int temp = nums[i];

            if (swapIndex == i) {
                result[i] = temp;
            } else {
                result[i] = result[swapIndex];
                result[swapIndex] = temp;
            }
        }

        return result;
    }
}

/**
 * Your Solution object will be instantiated and called as such:
 * Solution obj = new Solution(nums);
 * int[] param_1 = obj.reset();
 * int[] param_2 = obj.shuffle();
 */