136_single_number.md

136 - Single Number

leetcode link

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

Solution - xor trick

int singleNumber(vector<int>& nums) {
  return accumulate(next(nums.begin()), nums.end(), nums.front(), bit_xor<int>());
}