Description
https://leetcode.com/problems/reverse-only-letters/
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:
S.length <= 10033 <= S[i].ASCIIcode <= 122Sdoesn’t contain\or"
Explanation
Two pointers technique to swap alphabetical letters.
Python Solution
class Solution:
def reverseOnlyLetters(self, S: str) -> str:
i = 0
j = len(S) - 1
S_list = list(S)
while i < j:
if S_list[i].isalpha() and S_list[j].isalpha():
temp = S_list[j]
S_list[j] = S_list[i]
S_list[i] = temp
i += 1
j -= 1
elif S_list[i].isalpha():
j -= 1
elif S_list[j].isalpha():
i += 1
else:
i += 1
j -= 1
return "".join(S_list)- Time Complexity: O(N).
- Space Complexity: O(N).