Question

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

Difficulty:Medium

Category:HashTable, BitManipulation

Analyze

Solution

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