136. Single Number.cpp

/*
Link: https://leetcode.com/problems/single-number/

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

Note:

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

Example 1:

Input: [2,2,1]
Output: 1
Example 2:

Input: [4,1,2,1,2]
Output: 4
*/

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int ans=0;
        for (int i = 0; i < nums.size(); i++) 
        {
            ans = ans ^ nums[i];                // using the property: a xor a = 0 and a xor 0 = a, 
        }                                       //hence the all elements which occur twice shall become 0 and only left is our answer
        return ans;
    }
};

/*
T.C = O(n)
S.C = O(1)
*/