1 class Solution { 2 public: 3     string convert(string s, int nRows) { 4         if (nRows < 2) return s; 5         int len = s.size(), size = 2*nRows - 2; 6         string result; 7         for (int i = 0; i < nRows; i++) { 8             for (int j = i; j < len; j += size) { 9                 result += s[j];10                 if (i != 0 && i != nRows-1 && (j + size - 2*i) < len) {11                     result += s[j+size-2*i];12                 }13             }14         }15         return result;16     }17 };