题目描述
请实现一个函数，把字符串 s 中的每个空格替换成"%20"。
示例 1：
输入：s = "We are happy."
输出："We%20are%20happy."
限制：
0 <= s 的长度 <= 10000
class Solution:
def replaceSpace(self, s: str) -> str:
st = ''
for i in range(len(s)):
if s[i] == ' ':
st += '%20'
else:
st += s[i]
return st
