137. Single Number II

 1 public class Solution {
 2     public int singleNumber(int[] nums) {
 3         int onece = 0, twice = 0, xthree = 0;
 4         for (int i = 0; i < nums.length; i++) {
 5             twice |= onece & nums[i];
 6             onece ^= nums[i];
 7             
 8             xthree = ~(onece & twice);
 9             onece &= xthree;
10             twice &= xthree;
11         }
12         return (onece | twice);
13     }
14 }