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();
class Solution { private int[] arr; private Random generator; public Solution(int[] nums) { this.arr = new int[nums.length]; this.generator = new Random(System.nanoTime()); for (int i = 0; i < nums.length; i++) this.arr[i] = nums[i]; } /** 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[] copy = new int[arr.length]; int ind = 0; for (int i = 0; i < arr.length; i++) { while ((ind = generator.nextInt(arr.length)) < 0 || copy[ind] != 0) continue; copy[ind] = arr[i]; } return copy; } } /** * 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(); */
每次返回一个shuffle,就从0到arr.length,每个元素赋给新数组里的随机一个(这也叫shuffle?)