class Solution{
    public:
        string convert(string s,int numrows){
            if(numrows == 0|| numsrows>=s.length())
                return s;
            vector<vector<char>> rows(numrows);
            int index = 0, direc = 1;

            for(char c: s){
                rows[index].push_back(c);
                if(index == 0)
                    direc =1;
                else if(index == numrows -1)
                    direc = -1;
                index+=direc;
            }
            string res;
            for(const auto &row : rows)
                for(char c : row)
                    res+=c;

            return res;
        }
};