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917. Reverse Only Letters

Difficulty Topics

Description

Given a string s, reverse the string according to the following rules:

  • All the characters that are not English letters remain in the same position.
  • All the English letters (lowercase or uppercase) should be reversed.

Return s after reversing it.

 

Example 1:

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

Example 2:

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

Example 3:

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

 

Constraints:

  • 1 <= s.length <= 100
  • s consists of characters with ASCII values in the range [33, 122].
  • s does not contain '\"' or '\\'.

Solution

reverse-only-letters.py
class Solution:
    def reverseOnlyLetters(self, s: str) -> str:
        s = list(s)

        i, j = 0, len(s) - 1

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

        return "".join(s)