Issues with Implementing the Knuth-Morris-Pratt Algorithm in Java - Incorrect Pattern Matching Results on Overlapping Patterns
I just started working with I need some guidance on I'm converting an old project and Quick question that's been bugging me - I'm currently implementing the Knuth-Morris-Pratt (KMP) algorithm in Java for pattern matching, but I'm facing issues where the algorithm returns incorrect results when the pattern has overlapping sequences..... I’ve been following the standard KMP approach, but it seems that my implementation is not handling cases like the pattern "ABAB" correctly in the text "ABABABAB". Here’s a snippet of my code for the KMP search function: ```java public class KMPAlgorithm { public static void KMPSearch(String text, String pattern) { int[] lps = computeLPSArray(pattern); int i = 0; // index for text int j = 0; // index for pattern while (i < text.length()) { if (pattern.charAt(j) == text.charAt(i)) { i++; j++; } if (j == pattern.length()) { System.out.println("Found pattern at index " + (i - j)); j = lps[j - 1]; } else if (i < text.length() && pattern.charAt(j) != text.charAt(i)) { if (j != 0) { j = lps[j - 1]; } else { i++; } } } } private static int[] computeLPSArray(String pattern) { int[] lps = new int[pattern.length()]; int length = 0; int i = 1; while (i < pattern.length()) { if (pattern.charAt(i) == pattern.charAt(length)) { length++; lps[i] = length; i++; } else { if (length != 0) { length = lps[length - 1]; } else { lps[i] = 0; i++; } } } return lps; } } ``` In my tests with the input string `"ABABABAB"` and the pattern `"ABAB"`, I'm expecting to find the pattern at indices 0, 2, and 4. However, the algorithm only returns the first match at index 0 and misses the others, leading to missed results. I've tried modifying the way I update the index `j`, but it doesn’t seem to affect the outcome. I'm using Java 17 and running this in a standard console application. Any insights or suggestions for how to modify my implementation to handle overlapping patterns correctly would be greatly appreciated! I'm working on a service that needs to handle this. What's the best practice here? I've been using Java for about a year now. This issue appeared after updating to Java 3.9. Any suggestions would be helpful. Could this be a known issue?