LeetCode每日一题(Shuffle an Array)

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本文介绍如何使用 Rust 实现一个 Solution 类，该类可以对给定的整数数组进行随机洗牌，保证每次操作返回的数组都是等可能的排列。方法包括初始化、重置原始数组和进行随机化操作。适用于需要频繁随机数组的场景，同时满足性能和公平性要求。

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 <= 200
-106 <= nums[i] <= 106
All the elements of nums are unique.
At most 5 * 104 calls in total will be made to reset and shuffle.

代码(Rust):

use rand::{thread_rng, Rng};

struct Solution {
    origin: Vec<i32>,
    list: Vec<i32>,
}

/**
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
impl Solution {
    fn new(nums: Vec<i32>) -> Self {
        Self {
            origin: nums.clone(),
            list: nums,
        }
    }

    /** Resets the array to its original configuration and return it. */
    fn reset(&self) -> Vec<i32> {
        self.origin.clone()
    }

    /** Returns a random shuffling of the array. */
    fn shuffle(&mut self) -> Vec<i32> {
        let mut rng = thread_rng();
        for i in 0..self.list.len() {
            let j: usize = rng.gen_range(i, self.list.len());
            let tmp = self.list[i];
            self.list[i] = self.list[j];
            self.list[j] = tmp;
        }
        self.list.clone()
    }
}