844 Backspace String Compare.py

'''
Given two strings s and t, return true if they are equal when both are typed into empty text editors. '#' means a backspace character.
Note that after backspacing an empty text, the text will continue empty.

Example 1:

Input: s = "ab#c", t = "ad#c"
Output: true
Explanation: Both s and t become "ac".

Example 2:

Input: s = "ab##", t = "c#d#"
Output: true
Explanation: Both s and t become "".

Example 3:

Input: s = "a#c", t = "b"
Output: false
Explanation: s becomes "c" while t becomes "b".
 
Constraints:

1 <= s.length, t.length <= 200
s and t only contain lowercase letters and '#' characters.
 
Follow up: Can you solve it in O(n) time and O(1) space?
'''
class Solution:
    def backspaceCompare(self, s: str, t: str) -> bool:
        new_s = []
        new_t = []
        for val in s:
            if val == '#' and new_s:
                new_s.pop(-1)
            elif val != '#':
                new_s.append(val)
        for val in t:
            if val == '#' and new_t:
                new_t.pop(-1)
            elif val != '#':
                new_t.append(val)

        return new_s == new_t