Leetcode-Single Number II

#Leetcode

题目描述

Given an array of integers, every element appears three times except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

代码

	class Solution {
			public:
			    int singleNumber(int A[], int n) {
				// IMPORTANT: Please reset any member data you declared, as
				// the same Solution instance will be reused for each test case.
			    int once = 0;//记录%3余1的bit
				int twice = 0;//记录%3余2的bit
				for(int i = 0; i < n; i++)
				{
					twice |= once & A[i];   //或运算
					once ^= A[i];
					int not_three = ~(once & twice);
					once = not_three & once;
					twice = not_three & twice;
				}
				return once;    
			    }
			};