384. 打乱数组

384. 打乱数组

洗牌算法：第一次接触，感觉很奇怪。

System.arraycopy(nums,0,original,0,nums.length);

参数分别是原始数组，复制的原始数组开始下标，目标数组，目标数组的开始下标，复制的数组长度。

class Solution {
    int[] nums;
    int[] original;
    public Solution(int[] nums) {
        this.nums = nums;
        this.original = new int[nums.length];
        System.arraycopy(nums,0,original,0,nums.length);
    }
    
    public int[] reset() {
        System.arraycopy(original,0,nums,0,nums.length);
        return nums;
    }
    
    public int[] shuffle() {
        // 依次决定第i个元素，把它与第[i,n]的随机1个元素交换位置
        Random rd = new Random();
        for(int i = 0;i < nums.length;i++){
            int j = i + rd.nextInt(nums.length - i);
            int temp = nums[i];
            nums[i] = nums[j];
            nums[j] = temp;
        }
        return nums;
    }
}

/**
 * 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();
 */