137.cpp

#include<bits/stdc++.h>
using namespace std;

int singleNumber(vector<int>& nums) {
    int ones = 0;
    int twos = 0;

    for (const int num : nums) {
      ones ^= (num & ~twos);
      twos ^= (num & ~ones);
    }

    return ones;
  }
};

int main()
{
  return 0;
}