text: # -*- coding: utf-8 -*-
  """
  
     File Name：     replace_space
     Author :       jing
     Date：          2020/3/15
  
     将空格替换成%20
  """
  
  
  class Solution:
      # s 源字符串
      # O(n)的方法：计算字符串长度、空格长度，从后往前替换
      def replaceSpace(self, s):
          # write code here
          if s is None or s == "":
              return s
          else:
              return s.replace(" ", "%20")
  