Algorithm
Problem Name: 917. Reverse Only Letters
Problem Link: https://leetcode.com/problems/reverse-only-letters/
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 <= 100sconsists of characters with ASCII values in the range[33, 122].sdoes not contain'\"'or'\\'.
Code Examples
#1 Code Example with Java Programming
Code -
Java Programming
class Solution {
public String reverseOnlyLetters(String s) {
int start = 0;
int end = s.length() - 1;
char[] letters = s.toCharArray();
while (start < = end) {
while (start <= end && !Character.isLetter(s.charAt(start))) {
start++;
}
while (end >= start && !Character.isLetter(s.charAt(end))) {
end--;
}
if (start < = end) {
char temp = letters[start];
letters[start++] = letters[end];
letters[end--] = temp;
}
}
return String.valueOf(letters);
}
}
Input
s = "ab-cd"
Output
"dc-ba"
#2 Code Example with Javascript Programming
Code -
Javascript Programming
const reverseOnlyLetters = function(S) {
let start = 0
let end = S.length - 1
const arr = S.split("")
while (start < end) {
while (start < end && !chk(S.charCodeAt(start))) {
start++
}
while (start < end && !chk(S.charCodeAt(end))) {
end--
}
let tmp = S[end]
arr[end] = S[start]
arr[start] = tmp
start++
end--
}
return arr.join("")
}
function chk(num) {
const aCode = "a".charCodeAt(0)
const zCode = "z".charCodeAt(0)
const ACode = "A".charCodeAt(0)
const ZCode = "Z".charCodeAt(0)
if ((num >= aCode && num <= zCode) || (num >= ACode && num <= ZCode)) {
return true
} else {
return false
}
}
Input
s = "ab-cd"
Output
"dc-ba"
#3 Code Example with Python Programming
Code -
Python Programming
class Solution:
def reverseOnlyLetters(self, S):
r = [s for s in S if s.isalpha()]
return "".join(S[i] if not S[i].isalpha() else r.pop() for i in range(len(S)))
Input
s = "a-bC-dEf-ghIj"
Output
"j-Ih-gfE-dCba"
#4 Code Example with C# Programming
Code -
C# Programming
using System.Text;
namespace LeetCode
{
public class _0917_ReverseOnlyLetters
{
public string ReverseOnlyLetters(string S)
{
var sb = new StringBuilder();
var j = S.Length - 1;
for (int i = 0; i < S.Length; i++)
{
if (char.IsLetter(S[i]))
{
while (!char.IsLetter(S[j]))
j--;
sb.Append(S[j--]);
}
else
sb.Append(S[i]);
}
return sb.ToString();
}
}
}
Input
s = "a-bC-dEf-ghIj"
Output
"j-Ih-gfE-dCba"