The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
P   A   H   N
A P L S I I G
Y   I   R
And then read line by line: "PAHNAPLSIIGYIR"
Write the code that will take a string and make this conversion given a number of rows:
string convert(string s, int numRows);
Example 1:
Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"
Example 2:
Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P     I    N
A   L S  I G
Y A   H R
P     I
class Solution:
     def convert(self, s, numRows):
         """
         :type s: str
         :type numRows: int
         :rtype: str
         """
         if len(s) == 0 or numRows < 1:
             return ''
         if numRows == 1:
             return s
         maxStep = (numRows-1)*2
         reStr = ''
         for i in range(numRows):
             j = i
             step = maxStep-2*i
             while j < len(s):
                 reStr += s[j]
                 if step == 0:
                     j += maxStep
                 else:                    
                     j += step
                 step = maxStep-step
                 if step == 0:
                     step = maxStep
         return reStr
class Solution:
     def convert(self, s, numRows):
         """
         :type s: str
         :type numRows: int
         :rtype: str
         """
         if len(s) == 0 or numRows < 1:
             return ''
         if numRows == 1:
             return s
         maxStep = (numRows-1)*2
         reStr = ''
         for i in range(numRows):
             j = i
             step = maxStep-2*i
             while j < len(s):
                 reStr += s[j]
                 if step == 0:
                     j += maxStep
                 else:                    
                     j += step
                 step = maxStep-step
                 if step == 0:
                     step = maxStep
         return reStr