844. Backspace String Compare - LeetCode

class Solution1:
    def backspaceCompare(self, s: str, t: str) -> bool:
        S = '#'
        ss, st = [], []
        for c in s:
            if c != S:
                ss.append(c)
            elif ss:
                ss.pop()
        for c in t:
            if c != S:
                st.append(c)
            elif st:
                st.pop()
        return ss == st


class Solution:
    def backspaceCompare(self, s: str, t: str) -> bool:
        def go_left(string, pointer, backspace):
            S = '#'
            while pointer >= 0 and (backspace or string[pointer] == S):
                backspace += (-1) ** (string[pointer] != S)
                pointer -= 1
            return pointer, backspace

        ps, pt = len(s) - 1, len(t) - 1  # pointer
        bs, bt = 0, 0  # backspace
        while True:
            (ps, bs), (pt, bt) = go_left(s, ps, bs), go_left(t, pt, bt)
            if not (ps >= 0 and pt >= 0 and s[ps] == t[pt]):
                return ps == pt == -1
            ps -= 1
            pt -= 1