Today I have done leetcode's September LeetCoding Challenge with cpp.

September LeetCoding Challenge 14

Description

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

Solution

class Solution {
public:
  string reverseOnlyLetters(string s) {
    int begin = 0;
    int end = s.length() - 1;
    while(begin < end) {
      while(begin < end && !isalpha(s[begin])) begin += 1;
      while(begin < end && !isalpha(s[end])) end -= 1;
      if(begin < end) swap(s[begin], s[end]);
      begin += 1;
      end -= 1;
    }
    return s;
  }
};

// Accepted
// 115/115 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 65.04 % of cpp submissions (6 MB)