Problem Statement

Given an integer array nums where every element appears three times except for one, which appears exactly once. Find the single element and return it.

You must implement a solution with a linear runtime complexity and use only constant extra space.

Example 1:

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

Example 2:

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

Constraints:

• 1 <= nums.length <= 3 * 104
• 231 <= nums[i] <= 231 - 1
• Each element in nums appears exactly three times except for one element which appears once.

Problem Link

Single Number II - LeetCode

Reference Video

https://www.youtube.com/watch?v=cOFAmaMBVps&ab_channel=TECHDOSE

Code

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        
        int n = nums.size();
        
        int one = 0;//contains the element which occurred only once till the current 
// iteration
        int two = 0;//contains the element which occurred only twice till the current 
// iteration
        
        for(int num:nums)
        {
            one = (one^num)&(~two);
            two = (two^num)&(~one);
        }
        
        return one;
        
    }
};