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Refactor KMP and RabinKarp: Improve Reusability and Test Coverage (#7250)

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* first commit

* Running KMPTest and RabinKarpTest with fixed formatting

* now build failed error resolved

* now build failed error resolved 2

---------

Co-authored-by: Divyansh Saxena <divyanshsaxena@gmail.com>
Co-authored-by: Deniz Altunkapan <deniz.altunkapan@outlook.com>
This commit is contained in:
Divyansh Saxena
2026-02-01 20:21:13 +05:30
committed by GitHub
parent f3fd9ca385
commit dfaa495639
4 changed files with 119 additions and 45 deletions
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27
src/main/java/com/thealgorithms/strings/KMP.java
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@@ -1,5 +1,8 @@
package com.thealgorithms.strings;
import java.util.ArrayList;
import java.util.List;
/**
* Implementation of Knuth–Morris–Pratt algorithm Usage: see the main function
* for an example
@@ -8,16 +11,19 @@ public final class KMP {
private KMP() {
}
// a working example
/**
* find the starting index in string haystack[] that matches the search word P[]
*
* @param haystack The text to be searched
* @param needle The pattern to be searched for
* @return A list of starting indices where the pattern is found
*/
public static List<Integer> kmpMatcher(final String haystack, final String needle) {
List<Integer> occurrences = new ArrayList<>();
if (haystack == null || needle == null || needle.isEmpty()) {
return occurrences;
}
public static void main(String[] args) {
final String haystack = "AAAAABAAABA"; // This is the full string
final String needle = "AAAA"; // This is the substring that we want to find
kmpMatcher(haystack, needle);
}
// find the starting index in string haystack[] that matches the search word P[]
public static void kmpMatcher(final String haystack, final String needle) {
final int m = haystack.length();
final int n = needle.length();
final int[] pi = computePrefixFunction(needle);
@@ -32,10 +38,11 @@ public final class KMP {
}
if (q == n) {
System.out.println("Pattern starts: " + (i + 1 - n));
occurrences.add(i + 1 - n);
q = pi[q - 1];
}
}
return occurrences;
}
// return the prefix function