384. Shuffle an Array

遍历原数组，当前I，然后随机nextInt(length-i)，两个SWAP，就表示随便选了一个放到I了，然后再看I+1，I+2。。到最后就行了。

int[] origin;
    int[] res;
    Random rdm = new Random();
    public Solution(int[] nums) 
    {
        origin = nums;
        res = Arrays.copyOf(nums,nums.length);
        
    }
    
    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        return origin;
    }
    
    /** Returns a random shuffling of the array. */
    public int[] shuffle() 
    {
        
        int length = origin.length;
        if(length == 0) return res;
        for(int m = 0 ; m < origin.length;m++)
        {
            int rdmI = rdm.nextInt(length-m);
            swap(res,m,rdmI);

        }
        return res;
    }

    public void swap(int[] res, int m, int rdmI)
    {
        int temp = res[m];
        res[m] = res[rdmI];
        res[rdmI] = temp;
    }