Java实现 LeetCode 384 打乱数组

384. 打乱数组

打乱一个没有重复元素的数组。

示例:

// 以数字集合 1, 2 和 3 初始化数组。

int[] nums = {1,2,3};

Solution solution = new Solution(nums);

// 打乱数组 [1,2,3] 并返回结果。任何 [1,2,3]的排列返回的概率应该相同。

solution.shuffle();

// 重设数组到它的初始状态[1,2,3]。

solution.reset();

// 随机返回数组[1,2,3]打乱后的结果。

solution.shuffle();

class Solution {

     private int[] nums;
    private int[] originalNums;

    public Solution(int[] nums) {
        this.nums = nums;
        this.originalNums = Arrays.copyOf(nums, nums.length);
    }

    /**
     * Resets the array to its original configuration and return it.
     */
    public int[] reset() {
        return this.originalNums;
    }

    /**
     * Returns a random shuffling of the array.
     */
    public int[] shuffle() {
        Random random = new Random();
        for (int i = 0; i < nums.length / 2; i++) {
            // 每次只需拿第一个元素进行交换即可
            swap(nums, 0, random.nextInt(nums.length));
        }
        return nums;
    }

    private void swap(int[] nums, int i, int j) {
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }
}

/**
 * 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();
 */