From b02859b3b52ef4fac656ceba248fbc2d0229d2b1 Mon Sep 17 00:00:00 2001 From: Beck-berry Date: Sat, 7 Mar 2020 11:00:34 +0100 Subject: [PATCH 1/5] copy source code from master branch --- src/main/java/com/others/KMP.java | 57 +++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 src/main/java/com/others/KMP.java diff --git a/src/main/java/com/others/KMP.java b/src/main/java/com/others/KMP.java new file mode 100644 index 000000000000..e883076759ff --- /dev/null +++ b/src/main/java/com/others/KMP.java @@ -0,0 +1,57 @@ +package Others; + +/** + * Implementation of Knuth–Morris–Pratt algorithm + * Usage: see the main function for an example + */ +public class KMP { + //a working example + 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); + int q = 0; + for (int i = 0; i < m; i++) { + while (q > 0 && haystack.charAt(i) != needle.charAt(q)) { + q = pi[q - 1]; + } + + if (haystack.charAt(i) == needle.charAt(q)) { + q++; + } + + if (q == n) { + System.out.println("Pattern starts: " + (i + 1 - n)); + q = pi[q - 1]; + } + } + } + + // return the prefix function + private static int[] computePrefixFunction(final String P) { + final int n = P.length(); + final int[] pi = new int[n]; + pi[0] = 0; + int q = 0; + for (int i = 1; i < n; i++) { + while (q > 0 && P.charAt(q) != P.charAt(i)) { + q = pi[q - 1]; + } + + if (P.charAt(q) == P.charAt(i)) { + q++; + } + + pi[i] = q; + + } + return pi; + } +} \ No newline at end of file From ddd43569b873d722bf99ab0b9c5ed69ddbe92cbf Mon Sep 17 00:00:00 2001 From: Beck-berry Date: Sat, 7 Mar 2020 12:06:43 +0100 Subject: [PATCH 2/5] fix maven url --- build.gradle | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/build.gradle b/build.gradle index 04d375e31c9b..3bf4879fac64 100644 --- a/build.gradle +++ b/build.gradle @@ -5,7 +5,7 @@ plugins { repositories { mavenLocal() maven { - url = 'http://repo.maven.apache.org/maven2' + url = 'https://repo.maven.apache.org/maven2' } } From a3e0d7c2a947b312e077380b4bb22cfe9ecedec8 Mon Sep 17 00:00:00 2001 From: Beck-berry Date: Sat, 7 Mar 2020 12:07:02 +0100 Subject: [PATCH 3/5] fix package route --- src/main/java/com/others/KMP.java | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/main/java/com/others/KMP.java b/src/main/java/com/others/KMP.java index e883076759ff..3a5091e259b4 100644 --- a/src/main/java/com/others/KMP.java +++ b/src/main/java/com/others/KMP.java @@ -1,4 +1,4 @@ -package Others; +package com.others; /** * Implementation of Knuth–Morris–Pratt algorithm From bdd9b1a00d55c16cffc01e5d212b1828afe03d4d Mon Sep 17 00:00:00 2001 From: Beck-berry Date: Sat, 14 Mar 2020 18:45:03 +0100 Subject: [PATCH 4/5] clean code --- src/main/java/com/others/KMP.java | 67 +++++++++++++++++-------------- 1 file changed, 36 insertions(+), 31 deletions(-) diff --git a/src/main/java/com/others/KMP.java b/src/main/java/com/others/KMP.java index 3a5091e259b4..0123c8fb5a9e 100644 --- a/src/main/java/com/others/KMP.java +++ b/src/main/java/com/others/KMP.java @@ -1,55 +1,60 @@ package com.others; +import java.util.ArrayList; /** - * Implementation of Knuth–Morris–Pratt algorithm - * Usage: see the main function for an example + * Implementation of the Knuth–Morris–Pratt algorithm */ public class KMP { - //a working example - 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(); + /** + * KMPmatcher method finds if any string "needle" is in the string "haystack" and returns the index of its first letter for all occurrencies. + * @param haystack string in which the method is searching + * @param needle string which the method is searching for + * @return an ArrayList of starting indexes of the haystack that matches the searched needle + */ + public static ArrayList KMPmatcher(final String haystack, final String needle) { + final int haystackLength = haystack.length(); + final int needleLength = needle.length(); final int[] pi = computePrefixFunction(needle); - int q = 0; - for (int i = 0; i < m; i++) { - while (q > 0 && haystack.charAt(i) != needle.charAt(q)) { - q = pi[q - 1]; + int matchingLength = 0; + ArrayList startingIndexes = new ArrayList<>(); + for (int i = 0; i < haystackLength; i++) { + while (matchingLength > 0 && haystack.charAt(i) != needle.charAt(matchingLength)) { + matchingLength = pi[matchingLength - 1]; } - if (haystack.charAt(i) == needle.charAt(q)) { - q++; + if (haystack.charAt(i) == needle.charAt(matchingLength)) { + matchingLength++; } - if (q == n) { - System.out.println("Pattern starts: " + (i + 1 - n)); - q = pi[q - 1]; + if (matchingLength == needleLength) { + startingIndexes.add(i + 1 - needleLength); + matchingLength = pi[matchingLength - 1]; } } + return startingIndexes; } - // return the prefix function + /** + * The computePrefixFunction method gets the prefix function of the given string. + * @param P string (this should be the needle in the KNP) + * @return an array of indexes of the given sting where it matches itself + */ private static int[] computePrefixFunction(final String P) { - final int n = P.length(); - final int[] pi = new int[n]; + final int stringLength = P.length(); + final int[] pi = new int[stringLength]; pi[0] = 0; - int q = 0; - for (int i = 1; i < n; i++) { - while (q > 0 && P.charAt(q) != P.charAt(i)) { - q = pi[q - 1]; + int matchingLength = 0; + for (int i = 1; i < stringLength; i++) { + while (matchingLength > 0 && P.charAt(i) != P.charAt(matchingLength)) { + matchingLength = pi[matchingLength - 1]; } - if (P.charAt(q) == P.charAt(i)) { - q++; + if (P.charAt(i) == P.charAt(matchingLength)) { + matchingLength++; } - pi[i] = q; + pi[i] = matchingLength; } return pi; From 62e2864e80618b735a84f164adbb3e5a21707197 Mon Sep 17 00:00:00 2001 From: Beck-berry Date: Sat, 14 Mar 2020 19:09:13 +0100 Subject: [PATCH 5/5] add test to KMP --- src/test/java/com/others/KMPTest.java | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 src/test/java/com/others/KMPTest.java diff --git a/src/test/java/com/others/KMPTest.java b/src/test/java/com/others/KMPTest.java new file mode 100644 index 000000000000..fc845d80782b --- /dev/null +++ b/src/test/java/com/others/KMPTest.java @@ -0,0 +1,22 @@ +package com.others; + +import org.junit.jupiter.api.Assertions; +import org.junit.jupiter.api.Test; + +import java.util.ArrayList; + +class KMPTest { + + @Test + void testKMP() { + KMP kmp = new KMP(); + + ArrayList result = new ArrayList<>(); + result.add(0); + result.add(1); + Assertions.assertEquals(result, kmp.KMPmatcher("AAAAABAAABA", "AAAA"), "Incorrect Conversion"); + + ArrayList result2 = new ArrayList<>(); + Assertions.assertEquals(result2, kmp.KMPmatcher("ABABABA", "AAAA"), "Incorrect Conversion"); + } +}