Single Number

Problem Statement - link #

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.

Examples #

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 * 10^4
• -3 * 104 <= nums[i] <= 3 * 10^4
• Each element in the array appears twice except for one element which appears only once.

Solutions #

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int res = nums[0];
        for(int i=1; i<nums.size(); i++)
            res ^= nums[i];
        return res;
    }
};