题目描述：

方法一：

class Solution:     def convert(self, s: str, numRows: int) -> str:         if not s:             return ""         if numRows == 1:            return s         s_Rows = [""] * numRows         i = 0         n = len(s)         while i < n:             for j in range(numRows):                 if i < n:                     s_Rows[j] += s[i]                     i += 1             for j in range(numRows-2,0,-1):                 if i < n:                     s_Rows[j] += s[i]                     i += 1         return "".join(s_Rows)

方法二：

class Solution:     def convert(self, s: str, numRows: int) -> str:        if not s:             return ""         if numRows == 1:            return s         split_s_len = numRows * 2 - 2         data = []         n = len(s)         for i in range(0, n,split_s_len):             data.append(s[i:i+split_s_len])            #print(data)         res = ""         for i in range(numRows):             for tmp in data:                 if i < len(tmp):                     if i == 0 or i == numRows-1:                         res += tmp[i]                     else:                         res += tmp[i]                         if split_s_len -i < len(tmp):                             res += tmp[split_s_len-i]         return res