136. Single Number

 1 class Solution {
 2 public:
 3     int singleNumber(vector<int>& nums) {
 4         int num = 0;
 5         for (const auto& item : nums) {
 6             num ^= item;
 7         }
 8         return num;
 9     }
10 };

 1 class Solution {
 2 public:
 3     int singleNumber(vector<int>& nums) {
 4         int num = 0;
 5         for (const auto& item : nums) {
 6             num ^= item;
 7         }
 8         return num;
 9     }
10 };