136. Single Number

Problem Statement

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

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

Example 1:

Input: nums = [2,2,1]
Output: 1

Example 2:

Input: nums = [4,1,2,1,2]
Output: 4

Example 3:

Input: nums = [1]
Output: 1

Constraints:

1 <= nums.length <= 3 * 104
-3 * 104 <= nums[i] <= 3 * 104
Each element in the array appears twice except for one element which appears only once.

Intuition

We can use exor operation ; 
This works because all elements are twice and in exor 1^1=0 and 2^2=0
So on , all elements twice are nullified and only one remains

Video Links

Approach 1:

Xor

C++

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int f=0;

        for(int i=0;i<nums.size();i++){
            f^=nums[i];
        }

        return f;
    }
};

Approach 2:

C++

Approach 3:

C++

Approach 4:

C++