136. Single Number

• Difficulty: Easy

• Topics: Hash Table, Bit Manipulation

• Similar Questions:

  • Single Number II

  • Single Number III

  • Missing Number

  • Find the Duplicate Number

  • Find the Difference

Problem:

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

Solutions:

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int ret = 0;
        for (auto num : nums) {
            ret ^= num;
        }

        return ret;
    }
};