leetcode844 Backspace String Compare

"""
Given two strings S and T, return if they are equal when both are typed into empty text editors. # means a backspace character.
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".
"""
"""
简单题通过
"""
class Solution:
    def backspaceCompare(self, S, T):
        """
        :type S: str
        :type T: str
        :rtype: bool
        """
        return self._back(S) == self._back(T)
    def _back(self, string):
        stack = []
        for i in range(len(string)):
            if string[i] == '#':
                if stack: #这里重要，需要判断stack不为空，对于这种[#a#c]输入
                    stack.pop()
                continue
            stack.append(string[i])
        return stack