LeetCode in Kotlin

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

import kotlin.random.Random

@Suppress("kotlin:S2245")
class Solution(private val nums: IntArray) {
    // Resets the array to its original configuration and return it.
    fun reset(): IntArray {
        return nums
    }

    // Returns a random shuffling of the array.
    fun shuffle(): IntArray {
        val shuffled = nums.clone()
        for (i in nums.size - 1 downTo 1) {
            val j: Int = Random.nextInt(i + 1)
            swap(shuffled, i, j)
        }
        return shuffled
    }

    private fun swap(shuffled: IntArray, i: Int, j: Int) {
        val tmp = shuffled[i]
        shuffled[i] = shuffled[j]
        shuffled[j] = tmp
    }
}

/*
 * Your Solution object will be instantiated and called as such:
 * var obj = Solution(nums)
 * var param_1 = obj.reset()
 * var param_2 = obj.shuffle()
 */

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