How to get count of max consecutive substring ab in given string abhwasababababuqabab

Question

How to get count of max consecutive substring ab in given string abhwasababababuqabab

Input: abhwasababababuqabab

Output: 4 how?

We have 4 consecutive ab at middle from 6th index to 13th index. At starting we have only 1 ab and at end we have 2 consecutive ab, but at middle we have 4 ab so we need to return max count of consecutive ab in the string.

public class MaxConsecutiveAbCount {
    public static int maxConsecutiveAbCount(String s) {
        int maxCount = 0;  // To store the maximum consecutive count
        int currentCount = 0;  // To store the current consecutive count

        for (int i = 0; i < s.length() - 1; i++) {
            // Check if the current and next characters form the substring "ab"
            if (s.substring(i, i + 2).equals("ab")) {
                currentCount++;
            } else {
                // Update maxCount if the current count is greater
                maxCount = Math.max(maxCount, currentCount);
                currentCount = 0;  // Reset current count for a non-"ab" substring
            }
        }

        // Update maxCount again in case the last substring is "ab"
        maxCount = Math.max(maxCount, currentCount);

        return maxCount;
    }

    public static void main(String[] args) {
        String inputString = "abhwasababababuqabab";
        int output = maxConsecutiveAbCount(inputString);
        System.out.println("Output: " + output);
    }
}

Answer 1

Your code doesn't work because every time it finds an instance of ab, it will check the next 2 characters, which would be b followed by another character. This would cause it to reset count.

This can be easily fixed by incrementing i with i++ after you find ab to skip the check on the b.

public class a {
    public static int maxConsecutiveAbCount(String s) {
        int maxCount = 0;  // To store the maximum consecutive count
        int currentCount = 0;  // To store the current consecutive count

        for (int i = 0; i < s.length() - 1; i++) {
            // Check if the current and next characters form the substring "ab"
            if (s.substring(i, i + 2).equals("ab")) {
                currentCount++;
                i++; // <--- ADD THIS LINE
            } else {
                // Update maxCount if the current count is greater
                maxCount = Math.max(maxCount, currentCount);
                currentCount = 0;  // Reset current count for a non-"ab" substring
            }
        }

        // Update maxCount again in case the last substring is "ab"
        maxCount = Math.max(maxCount, currentCount);

        return maxCount;
    }

    public static void main(String[] args) {
        String inputString = "abhwasababababuqabab";
        int output = maxConsecutiveAbCount(inputString);
        System.out.println("Output: " + output);
    }
}

Answer 2

You may use regex

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Regex {
    public static void main(String[] args) {
    
        // Find the first occurrence of any longest, repeated substring
            
        String s = "abhwasababababuqabab";
            
        Pattern pattern = Pattern.compile("((.+?)\\2+)");
        Matcher matcher = pattern.matcher(s);
        if (matcher.find() ) {
            System.out.println(matcher.group(2) + " in " + matcher.group(1));
            String text = matcher.group(1);
            String subtext = matcher.group(2);
            pattern = Pattern.compile(subtext);
            matcher = pattern.matcher(text);
            int c = 0;
            while(matcher.find()) {
               c++;
            }
            System.out.println(subtext + " occurs " + c + " times");    
        }
    }
}

Output:

ab in abababab
ab occurs 4 times

But if you only want to determine occurrence for 'ab' edit the code above with the following line for the regex pattern:

Pattern pattern = Pattern.compile("((ab)\\2+)");