剑指 Offer 05. 替换空格

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:
        res = ''
        for i in s:
            if i == ' ':
                res += '%20'
            else:
                res += i
        return res

class Solution:
    def replaceSpace(self, s: str) -> str:
        return s.replace(' ','%20')