844. Backspace String Compare

May 1, 2022

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.

code

class Solution:
    def backspaceCompare(self, s: str, t: str) -> bool:
        def build(s):
            stack = []
            for c in s:
                if c != "#": stack.append(c)
                elif stack: stack.pop()
            return "".join(stack)
                
        return build(s) == build(t)

code

class Solution(object):
    def backspaceCompare(self, S, T):
        def F(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(F(S), F(T)))