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：就是第i个元素，跟后面random [0,i]的元素进行互换即可，
注意Random random = new Random(); random.nextInt(i+1) [0,i]
class Solution { int[] original; int[] shuffleArray; public Solution(int[] nums) { int n = nums.length; original = new int[n]; shuffleArray = new int[n]; for(int i = 0; i < n; i++) { original[i] = shuffleArray[i] = nums[i]; } } /** Resets the array to its original configuration and return it. */ public int[] reset() { return this.original; } /** Returns a random shuffling of the array. */ public int[] shuffle() { Random random = new Random(); for(int i = shuffleArray.length - 1; i >=0 ; i--) { int index = random.nextInt(i+1); // nextInt(n) -> [0,i) swap(shuffleArray, index, i); } return shuffleArray; } private void swap(int[] A, int i, int j) { int temp = A[i]; A[i] = A[j]; A[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(); */
