Try to split all the numbers into two groups with each of the target one in different groups. Refer to for a nice explanation.

The code is written as follows.

1 class Solution { 2 public: 3     vector
     
       singleNumber(vector
      
       & nums) { 4         int t = 0, p, first = 0, second = 0; 5         for (int num : nums) t ^= num; 6         for (p = 0; p < 32; p++) 7             if ((t >> p) & 1) break; 8         for (int num : nums) { 9             if ((num >> p) & 1) first ^= num;10             else second ^= num;11         }12         return {first, second};13     }14 };