[leetcode]384. Shuffle an Array洗牌

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();

题意：

洗牌

Solution1：

code

 1 class Solution {
 2     int[] origin;
 3     int[] nums;
 4     Random random;
 5 
 6     public Solution(int[] nums) {
 7         origin = copy(nums);
 8         this.nums = copy(nums);
 9         random = new Random();
10     }
11 
12     /** Resets the array to its original configuration and return it. */
13     public int[] reset() {
14         nums = copy(origin);
15         random = new Random();
16         return nums;
17 
18     }
19 
20     /** Returns a random shuffling of the array. */
21     public int[] shuffle() {
22         final int n = nums.length;
23         int[] result = new int[n];
24 
25         for(int i = n; i>=1; i--){
26             int randomIdx = random.nextInt(i);
27             result[n - i] = nums[randomIdx];
28             int temp = nums[randomIdx];
29             nums[randomIdx] = nums[i - 1];
30             nums[i - 1] = temp;
31         }
32         return result;
33     }
34 
35     private int[] copy(int[] array){
36         int[] result = new int[array.length];
37         for(int i = 0; i < array.length; i++){
38             result[i] = array[i];
39         }
40         return result;
41     }
42 }
43 
44 /**
45  * Your Solution object will be instantiated and called as such:
46  * Solution obj = new Solution(nums);
47  * int[] param_1 = obj.reset();
48  * int[] param_2 = obj.shuffle();
49  */