LeetCode(Design)Shuffle an Array

Shuffle an Array

Shuffle a set of numbers without duplicates.

Example:

// Init an array with set 1, 2, and 3.
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned.
solution.shuffle();

// Resets the array back to its original configuration [1,2,3].
solution.reset();

// Returns the random shuffling of array [1,2,3].
solution.shuffle();

思路：题目没有什么太难的地方，主要是随机返回一个更改后的数组，这个地方需要一点技巧，可以用Random()函数来实现这样的功能，具体实现见代码。

class Solution {
      private int [] arr;
      private Random random;
    public Solution(int[] nums) {
        this.arr=nums;
        random=new Random();
    }
    
    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        return arr;
    }
    
    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
        int [] temp=arr.clone();
        for(int i=1;i<temp.length;i++){
            int j=random.nextInt(i+1);
            //随机交换arr[i],arr[j]的值
            int c=temp[i];
            temp[i]=temp[j];
            temp[j]=c;
        }
        return 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();