[JS] Shuffle an Array

🔒 문제 (LeetCode 384)

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.

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.

 

🌊 입출력

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]

 

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🔑 해결

🌌 알고리즘

/**
 * @param {number[]} nums
 */
var Solution = function(nums) {
    this.nums = nums
};

/**
 * @return {number[]}
 */
Solution.prototype.reset = function() {
    return this.nums
};

/**
 * @return {number[]}
 */
Solution.prototype.shuffle = function() {
    const random = [...this.nums]
    
    const swap = (i, j) => {
        [random[i], random[j]] = [random[j], random[i]]
    }
    
    for(let i = 0; i < random.length; i++) {
        const randIdx = Math.floor(Math.random() * random.length)
        swap(i, randIdx)
    }

    
    return random
};

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

class 사용

class Solution {
    constructor(nums) {
        this.nums = nums;
        this.random = [...nums];
    }
    
    reset() {
        return this.nums;
    }
    
    shuffle() {
        for(let i = 0; i < this.random.length; i++) {
            const randIdx = Math.floor(Math.random() * this.random.length);
            this.swap(i, randIdx);
        }
        return this.random;
    }
    
    swap(i, j) {
        [this.random[i], this.random[j]] = [this.random[j], this.random[i]]
    }
}