414. Third Maximum Number

    int thirdMax(vector<int>& nums) {
       set<int> s;
        for(int a:nums) s.insert(a);
        int res=0;
        for(auto it=s.rbegin();it!=s.rend();++it){
            if(res==2)
                return *it;
            res++;
        }
        return *(s.rbegin());
    }

    int thirdMax(vector<int>& nums) {
        long first=LONG_MIN,second=LONG_MIN,third=LONG_MIN;
        for(auto a : nums){
            if(a==first||a==second)
                continue;
            if(a>first)
            {
                third=second;
                second=first;
                first=a;
            }else if(a>second){
                third=second;
                second=a; 
            }else if(a>=third)
                third=a;    
        }
        return third==LONG_MIN?first:third;
    }