384. Shuffle An Array¶

Difficulty: Medium

384. Shuffle an Array

Medium

Given an integer array nums, design an algorithm to randomly shuffle the array. All permutations of the array should be equally likely as a result of the shuffling.

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 <= 50
-10⁶ <= nums[i] <= 10⁶
All the elements of nums are unique.
At most 10⁴ calls in total will be made to reset and shuffle.

Solution¶

class Solution {
    private int original[];
    private int shuffled[];
    public Solution(int[] nums) {
        original = new int[nums.length];
        shuffled = new int[nums.length];
        for (int i = 0; i < nums.length; i++) {
            original[i] = nums[i];
            shuffled[i] = nums[i];
        }
    }
    public int[] reset() {
        return original;
    }
    public int[] shuffle() {
        ArrayList<Integer> temp = new ArrayList<>();
        for (int ele : shuffled) temp.add(ele);
        Collections.shuffle(temp);
        for (int i = 0; i < temp.size(); i++) shuffled[i] = temp.get(i);
        return shuffled;
    }
}

/**
 * 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();
 */

Complexity Analysis¶

Time Complexity: O(?)
Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here