6_Zigzag_Conversion.py

'''
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):
        if numRows == 1:
            return s
        rows = [""] * numRows
        point,row = -1, 0
        for i in range(len(s)):
            rows[row]+=s[i]
            if (row == 0 or row==numRows-1):
                point *= -1
            row+=point
        return "".join(rows)