LeetCode 917: Reverse Only Letters Solution

Master LeetCode problem 917 (Reverse Only Letters), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

917. Reverse Only Letters

Easy

Two Pointers String

Problem Explanation

Explanation

To solve this problem, we can use a two-pointer approach. We will have one pointer starting from the beginning of the string and another pointer starting from the end of the string. We will iterate over the string and swap characters at the two pointers if they are both English letters. If one or both characters are not English letters, we will skip them and move the respective pointers.

Time complexity: O(n) where n is the length of the input string
Space complexity: O(n) for storing the characters in the resulting string

Solution Code

class Solution {
    public String reverseOnlyLetters(String s) {
        char[] chars = s.toCharArray();
        int left = 0, right = s.length() - 1;
        
        while (left < right) {
            if (!Character.isLetter(chars[left])) {
                left++;
            } else if (!Character.isLetter(chars[right])) {
                right--;
            } else {
                char temp = chars[left];
                chars[left] = chars[right];
                chars[right] = temp;
                left++;
                right--;
            }
        }
        
        return new String(chars);
    }
}

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