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 '\\'.
Solutions
Solution 1: Two Pointers
We use two pointers $i$ and $j$ to point to the head and tail of the string respectively. When $i < j$, we continuously move $i$ and $j$ until $i$ points to an English letter and $j$ points to an English letter, then we swap $s[i]$ and $s[j]$. Finally, we return the string.
The time complexity is $O(n)$, and the space complexity is $O(n)$, where $n$ is the length of the string.