384. 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();

解题要点：

正常遍历，swap当前数字和另一个random index的数字。

import java.util.Random;
class Solution {
    int[] out;
    int[] ori;
    Random random;
    public Solution(int[] nums) {
        random = new Random();
        out = nums.clone();
        ori = nums.clone();
    }
    
    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        return ori;
    }
    
    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
        for(int i = 0; i < out.length; i++){
            int j = random.nextInt(out.length - i) + i;
            swap(out, i, j);
        }
        return out;
    }
    
    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();
 */