README_CN.md

917. 仅仅反转字母

给定一个字符串 S，返回 “反转后的” 字符串，其中不是字母的字符都保留在原地，而所有字母的位置发生反转。

示例 1:

输入: "ab-cd"
输出: "dc-ba"

示例 2:

输入: "a-bC-dEf-ghIj"
输出: "j-Ih-gfE-dCba"

示例 3:

输入: "Test1ng-Leet=code-Q!"
输出: "Qedo1ct-eeLg=ntse-T!"

提示:

1. S.length <= 100
2. 33 <= S[i].ASCIIcode <= 122
3. S 中不包含 \ or "

题解 (Python)

1. 双指针

class Solution:
    def reverseOnlyLetters(self, S: str) -> str:
        S = list(S)
        i, j = 0, len(S) - 1

        while i < j:
            if S[i].isalpha() and S[j].isalpha():
                S[i], S[j] = S[j], S[i]
                i += 1
                j -= 1
            elif not S[i].isalpha():
                i += 1
            elif not S[j].isalpha():
                j -= 1

        return ''.join(S)

2. 栈

class Solution:
    def reverseOnlyLetters(self, S: str) -> str:
        stack = []
        ret = ""

        for ch in S:
            if ch.isalpha():
                stack.append(ch)

        for ch in S:
            if ch.isalpha():
                ret += stack.pop()
            else:
                ret += ch

        return ret