[String] Jianzhi Offer 05. Replace spaces

Title description :
Please implement a function to replace each space in the string s with "%20".

Example :
Input: s = "We are happy."
Output: "We%20are%20happy."

Solution :
In languages ​​such as Python and Java, strings are designed as "immutable" types, that is, a certain character of a string cannot be directly modified, and a new string needs to be created to implement it. And note that we cannot modify the value of the variable through the loop variable

class Solution:
    def replaceSpace(self, s: str) -> str:
        result = ""
        for i in s:
            if i == " ":
                result = result+"%20"
            else:
                result = result+i
        return result        

Use the list as the result, and finally convert it to a string and return it

class Solution:
    def replaceSpace(self, s: str) -> str:
        result = []
        for i in s:
            if i == " ":
                result.append("%20")
            else:
                result.append(i)
        return "".join(result)