2414. Length of the Longest Alphabetical Continuous Substring

Method 1

An alphabetical continuous string is a string consisting of consecutive letters in the alphabet. In other words, it is any substring of the string "abcdefghijklmnopqrstuvwxyz".
- For example, "abc" is an alphabetical continuous string, while "acb" and "za" are not.
Given a string s consisting of lowercase letters only, return the length of the longest alphabetical continuous substring.

Example 1

Input: s = "abacaba"
Output: 2
Explanation: There are 4 distinct continuous substrings: "a", "b", "c" and "ab".
"ab" is the longest continuous substring.

Example 2

Input: s = "abcde"
Output: 5
Explanation: "abcde" is the longest continuous substring.

Method 1

【O(n) time | O(1) space】

package Leetcode.GroupedLoop;

/**
 * @author zhengxingxing
 * @date 2025/04/09
 */
public class LengthOfTheLongestAlphabeticalContinuousSubstring {
    
    public static int longestContinuousSubstring(String s) {
        // Handle edge cases
        if (s == null || s.length() == 0){
            return 0;
        }

        // Initialize variables
        int n = s.length();          // Length of the string
        int maxLength = 1;           // Track maximum length found
        int i = 0;                   // Current position in string

        // Process string in groups
        while (i < n){
            int start = i;           // Start of current group

            // Extend the current group while characters are consecutive
            // i + 1 < n ensures we don't access beyond string bounds
            // charAt(i + 1) == charAt(i) + 1 checks if next char is consecutive
            while (i + 1 < n && s.charAt(i + 1) == s.charAt(i) + 1){
                i++;
            }

            // Calculate length of current group
            // Add 1 to include the starting character
            int groupLength = i - start + 1;

            // Update maximum length if current group is longer
            maxLength = Math.max(maxLength, groupLength);

            // Move to start of next group
            i++;
        }
        return maxLength;
    }

    public static void main(String[] args) {
        // Test Case 1: Multiple continuous substrings of different lengths
        String test1 = "abacaba";
        System.out.println("Test 1: " + test1);
        System.out.println("Expected: 2");
        System.out.println("Actual: " + longestContinuousSubstring(test1));
        System.out.println();

        // Test Case 2: Perfect continuous string
        String test2 = "abcde";
        System.out.println("Test 2: " + test2);
        System.out.println("Expected: 5");
        System.out.println("Actual: " + longestContinuousSubstring(test2));
        System.out.println();

        // Test Case 3: Single character
        String test3 = "a";
        System.out.println("Test 3: " + test3);
        System.out.println("Expected: 1");
        System.out.println("Actual: " + longestContinuousSubstring(test3));
        System.out.println();

        // Test Case 4: Descending order string
        String test4 = "zyxw";
        System.out.println("Test 4: " + test4);
        System.out.println("Expected: 1");
        System.out.println("Actual: " + longestContinuousSubstring(test4));
        System.out.println();

        // Test Case 5: Multiple continuous segments
        String test5 = "abcdeijkl";
        System.out.println("Test 5: " + test5);
        System.out.println("Expected: 5");
        System.out.println("Actual: " + longestContinuousSubstring(test5));
        System.out.println();
    }
}

Method 1

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