137. Single Number II.cpp

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int ones = 0, twos = 0;
        for (int num : nums) {
            ones = (ones ^ num) & ~twos;
            twos = (twos ^ num) & ~ones;
        }
        return ones;
    }
};

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        unordered_map<int,int>mp;
        for(auto it : nums){
            mp[it]++;
        }
        int ans = 0;
        for(auto it : mp){
            if(it.second == 1){
                ans += it.first;
            }
        }
        return ans;
    }
};