Single Number II

Desicription

Given a non-empty array of integers, every element appears three times except for one, which appears exactly once. Find that single one.

Note:

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

Example 1:

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Input: [2,2,3,2]
Output: 3

Example 2:

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Input: [0,1,0,1,0,1,99]
Output: 99

Solution

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class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int a = 0;
        int b = 0;
        for(auto it : nums) {
            a = (a ^ it) & ~b;
            b = (b ^ it) & ~a;
        }
        return a;
    }
};