"""
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 BackspaceStringCompare:
    def backspaceCompare(self, s: str, t: str) -> bool:

        def build(input):
            stack = []
            for c in input:
                if c != '#':
                    stack.append(c)
                elif stack:
                    stack.pop()
            return ''.join(stack)

        return build(s) == build(t)
