1. What I learned

    a. .lower()

        It changes every character to lower case. But using ‘.lower()’ takes a lot of time.
        ex) print(‘HELLO’.lower()) –> ‘hello’

    b. ord()

        It returns an integer representing the Unicode character.
        ex) print(ord(‘a)) –> 97

2. How I sloved

    Using ‘.lower()’ took longer, so I approached all the letters. I checked if the letters were capital letters. In capital letters I changed the letter to Unicode and added 32. If it wasn’t capital letters, I just connected them.

3. Code

class Solution:
    def toLowerCase(self, str: str) -> str:
        return ''.join([chr(ord(c)+32) if c.isupper() else c for c in str])
class Solution:
    def toLowerCase(self, str: str) -> str:
        return str.lower()

4. Result

        Runtime : 16 ms(99.52%), Memory usage : 12.9 MB(100.00%)
        (Runtime can be different by a system even if it is a same code.)

Check out the my GitHub repo for more info on the code. If you have questions, you can leave a reply on this post.