day_9.py

'''
Problem Statement:
Given two strings S and T, return 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 = "#a#c"
Output: true
Explanation: Both S and T become "c".
Example 4:

Input: S = "a#c", T = "b"
Output: false
Explanation: S becomes "c" while T becomes "b".
Note:

1 <= S.length <= 200
1 <= 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?
'''

# Solution:

from itertools import zip_longest
class Solution:
    def backspaceCompare(self, S: str, T: str) -> bool:
        def temp(S):
            skip = 0
            for x in reversed(S):
                if x == '#':
                    skip += 1
                elif skip:
                    skip -= 1
                else:
                    yield x

        return all(x == y for x, y in itertools.zip_longest(temp(S), temp(T)))