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

Difficulty: interview

Starter code:

class Solution:
    def convert(self, s: str, numRows: int) -> str:
        

Solutions:
class Solution(object):
     def convert(self, s, numRows):
         """
         :type s: str
         :type numRows: int
         :rtype: str
         """
         if numRows == 1:
             return s
         zigzag = ['' for i in range(numRows)] 
         row = 0                                
         step = 1                              
         for c in s:
             if row == 0:
                 step = 1
             if row == numRows - 1:
                 step = -1
             zigzag[row] += c
             row += step
         return ''.join(zigzag)

class Solution:
     def convert(self, s, numRows):
         """
         :type s: str
         :type numRows: int
         :rtype: str
         """
         if numRows == 1 or numRows >= len(s):
             return s
 
         result = [''] * numRows
 
         index, step = 0, 1
 
         for c in s:
             result[index] += c
             if index == 0:
                 step = 1
             elif index == numRows-1:
                 step = -1
             index += step
 
         return ''.join(result)


class Solution:
     def convert(self, s, numRows):
         """
         :type s: str
         :type numRows: int
         :rtype: str
         """
         if numRows == 1 or numRows >= len(s):
             return s
 
         list_string = [''] * numRows
         index, step = 0, 1
 
         for i in s:
             list_string[index] += i
             if index == 0:
                 step = 1
             elif index == numRows -1:
                 step = -1
             index += step
 
         return ''.join(list_string)

class Solution:
     def convert(self, s, nRows):
         """
         :type s: str
         :type numRows: int
         :rtype: str
         """
         if nRows==1: return s
         # nRows strings, each letter of s falls into a string
         tmp=['' for i in range(nRows)]
         index=-1; step=1
         for i in range(len(s)):
             index+=step
             if index==nRows:
                 index-=2; step=-1
             elif index==-1:
                 index=1; step=1
             tmp[index]+=s[i]
         return ''.join(tmp)

class Solution:
     def convert(self, s, nRows):
         if nRows==1: return s
         tmp=['' for i in range(nRows)]
         index=-1; step=1
         for i in range(len(s)):
             index+=step
             if index==nRows:
                 index-=2; step=-1
             elif index==-1:
                 index=1; step=1
             tmp[index]+=s[i]
         return ''.join(tmp)

class Solution:
     def convert(self, s, numRows):
         """
         :type s: str
         :type numRows: int
         :rtype: str
         """
         if numRows == 1:
             return s
         count = len(s)
         if count <= 1:
             return s
 
         result = []
         deltSmall = numRows - 1
         deltBig = 2 * deltSmall
         for i in range(0, numRows):
             k = i
             if i == 0 or i == deltSmall:
                 while k < count:
                     result.append(s[k])
                     k += deltBig
             else:
                 while k < count:
                     top = k - k % deltSmall
                     bottom = top + deltSmall
                     result.append(s[k])
                     nextk = 2 * bottom - k
                     if nextk < count:
                         result.append(s[nextk])
                     k += deltBig
 
         return "".join(result)

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