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();
【384.|384. Shuffle an Array】一刷
题解：类似于蓄水池算法
如果是第i个数字，有1/i的几率被留下。保证每个数字出现在每个位置的几率相同。
class Solution {
private int[] nums;
private Random random;
public Solution(int[] nums) {
this.nums = nums;
random = new Random();
}/** Resets the array to its original configuration and return it. */
public int[] reset() {
return nums;
}/** Returns a random shuffling of the array. */
public int[] shuffle() {
if(nums == null) return null;
int[] a = nums.clone();
for(int j = 1;
j < a.length;
j++) {
int i = random.nextInt(j + 1);
swap(a, i, j);
}
return a;
}private void swap(int[] a, int i, int j) {
int t = a[i];
a[i] = a[j];
a[j] = t;
}
}/**
* 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();
*/
