Description:

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   NA P L S I I GY   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);

　　

Examples:

Input: s = "PAYPALISHIRING", numRows = 3Output: "PAHNAPLSIIGYIR"

Input: s = "PAYPALISHIRING", numRows = 4Output: "PINALSIGYAHRPI"Explanation:P     I    NA   L S  I GY A   H RP     I　

Solutions:

 

class Solution(object):    def convert(self, s, numRows):        """        :type s: str        :type numRows: int        :rtype: str        """        if numRows == 1 or numRows >= len(s):  # 如果“行”数为一或者字母数小于“行”数            return s        L = [''] * numRows  #        index, step = 0, 1        for x in s:            L[index] += x   # 不太好理解？            if index == 0:                step = 1            elif index == numRows -1:                step = -1            index += step        return ''.join(L)