Practice Shuffle an Array

Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.

Medium#384

LeetCode Problem

Shuffle an Array

Array Math Design Randomized

Problem Statement

Solution(nums) stores an array of distinct integers. reset() returns its original ordering. shuffle() returns a permutation, with every possible permutation equally likely. Practice approach: Keep an untouched copy for reset. Apply Fisher-Yates to a working copy: at position i, swap with a uniformly chosen position from i through the last index. Restricting the random range as it shrinks makes each permutation equally likely. Randomly sorting by a comparator does not provide the same guarantee. Test that reset still works after multiple shuffles.

Source: Shuffle an Array on LeetCode. Use the original task for its coding environment and submissions.

Examples

# Example 1

Input

["Solution","shuffle","reset","shuffle"]
[[[4,7,9]],[],[],[]]

Output

[null,[7,9,4],[4,7,9],[9,4,7]]

Explanation

The two shown permutations are possible outcomes; each of the six permutations must be equally likely. reset always returns [4,7,9].

Constraints

1 <= nums.length <= 50

-10^6 <= nums[i] <= 10^6

Array values are distinct.

At most 10^4 total reset and shuffle calls.

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