ZigZag.cpp

class Solution {
public:
    string convert(string s, int num) {
        int len = s.size();
        string finalStr;
        if(num == 1||len<=1) return s;   
        int k = 2 * num - 2;
        for(int i = 0; i< num; i++)
        {
            for(int j = 0; i + j<len; j = j + k)
            {
                finalStr.push_back(s[i+j]);
                // get rid of the first and last line
                if(i!=0 && (i!= num - 1) && (j + k - i < len);
                    finalStr.push_back(s[j+k - i]);
            }
        }
        return finalStr;
    }
};