将字符串中的字符按Z字形排列，按行输出

示例1：

　　Input: s = "PAYPALISHIRING", numRows = 3  

       

　　Output: "PAHNAPLSIIGYIR"

示例2：

Python解决方案：

    def convert(self, s, numRows):""":type s: str:type numRows: int:rtype: str"""if len(s) <= numRows or numRows==1 :return ss_dict = {i:"" for i in range(numRows)}unit = 2*numRows - 2for i in range(len(s)):remain = i%unitif remain <= numRows - 1:s_dict[remain] += s[i]else:pos = unit - remains_dict[pos] += s[i]out = ""for i in range(numRows):out += s_dict[i]return out