[leetcode] 917. Reverse Only Letters

Description

Given a string S, return the “reversed” string where all characters that are not a letter stay in the same place, and all letters reverse their positions.

Example 1:

Input: "ab-cd"
Output: "dc-ba"

Example 2:

Input: "a-bC-dEf-ghIj"
Output: "j-Ih-gfE-dCba"

Example 3:

Input: "Test1ng-Leet=code-Q!"
Output: "Qedo1ct-eeLg=ntse-T!"

Note:

1. S.length <= 100
2. 33 <= S[i].ASCIIcode <= 122
3. S doesn’t contain \ or "

分析

题目的意思是：只将字符串中字母部分进行翻转，其它保持不变。思路也很直接，翻转之后，原位置相应有字母的位置填上翻转的字符就行了。我看了一下答案，用了栈，其他思路基本一致。

代码

class Solution:
    def solve(self,ch):
        if((ch>='a' and ch<='z') or (ch>='A' and ch<='Z')):
            return True
        return False
        
    def reverseOnlyLetters(self, S: str) -> str:
        n=len(S)
        S1=list(reversed(S))
        i=0
        j=0
        res=''
        while(i<n):
            if(self.solve(S[i])):
                while(not self.solve(S1[j])):
                    j+=1
                res+=S1[j]
                j+=1
            else:
                res+=S[i]
            i+=1
        return res

参考文献

​​[LeetCode] Solution​​