143、打乱数组

题目描述：
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();

思路：这里我直接调用Collections的shuffle方法，进行调用
感觉没啥技术含量。。。

class Solution {
int solution[] = null;
	int solution2[] = null;
    public Solution(int[] nums) {
        solution = nums;
        solution2 = new int[nums.length];
        int index = 0;
        for (int i : nums) {
			solution2[index++] = i;
		}
    }
    
    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        return solution2;
    }
    
    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
    	List<Integer> tem = new ArrayList<>();
    	for (Integer integer : solution) {
			tem.add(integer);
		}
    	Collections.shuffle(tem);
    	int index = 0;
    	for (Integer integer : tem) {
			solution[index++] = integer;
		}
        return solution;
    }
}

/**
 * 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();
 */

参考别人手动实现的

class Solution {

    private int[] source;
    
    public Solution(int[] nums) {
        source = Arrays.copyOf(nums, nums.length);
    }
    
    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        return Arrays.copyOf(source, source.length);
    }
    
    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
        int[] target = Arrays.copyOf(source, source.length);
        
        int length = target.length;
        
        for (int i = length - 1; i > 0; i--) {
            // 随机[0-i]选一个数放在末尾，然后末尾依次减小，可以是自身i所以nextInt中是i+1
            int randomIndex = new Random().nextInt(i+1);
            int temp = target[i];
            target[i] = target[randomIndex];
            target[randomIndex] = temp;
        }
        
        return target;
    }
}

参考官网的解释，使用洗牌算法
添加链接描述