How to implement Boyer-Moore algorithm using java
How to implement the Boyer-Moore algorithm using Java
Introduction:
In computer science, string matching is a common task. The string matching algorithm is the key to solving this problem. One of the efficient string matching algorithms is the Boyer-Moore algorithm. This article will introduce how to use Java language to implement this algorithm, and attach specific code examples.
The principle of Boyer-Moore algorithm:
Boyer-Moore algorithm is a multi-pattern string matching algorithm. It completes matching by preprocessing the pattern string and combining good suffix rules and bad character rules. The core idea is to skip unmatched characters as much as possible during the matching process between the pattern string and the string to be matched, thereby improving the matching efficiency.
Specific implementation steps:
-
Preprocessing pattern string:
First, we need to preprocess the pattern string and generate two arrays: bad character array and Nice suffix array.- Bad character array: stores the rightmost position of each character in the pattern string.
- Good suffix array: record the rightmost occurrence position of the suffix substring of the pattern string in the pattern string, and record whether this substring matches the prefix of the pattern string.
-
Matching process:
During the matching process, we start matching forward from the end of the string to be matched.- First, align the end of the pattern string with the end of the string to be matched, and try to match.
- If the match is successful, return the starting position of the match, otherwise move the position of the pattern string according to the bad character and good suffix rules to continue matching.
The specific code is as follows:
import java.util.Arrays; public class BoyerMoore { private static final int NO_OF_CHARS = 256; private int[] badCharShift; private int[] suffixShift; private boolean[] goodSuffix; public void preProcessPattern(String pattern) { int m = pattern.length(); // 初始化数组 badCharShift = new int[NO_OF_CHARS]; suffixShift = new int[m + 1]; goodSuffix = new boolean[m + 1]; Arrays.fill(badCharShift, -1); for (int i = 0; i < m; i++) { badCharShift[pattern.charAt(i)] = i; } int f = 0; int g = 0; suffixShift[m] = m + 1; for (int i = m - 1; i >= 0; i--) { if (i > f && suffixShift[i + m - f] < i - f) { suffixShift[i] = suffixShift[i + m - f]; } else { if (i < f) { f = i; } g = i; while (f >= 0 && pattern.charAt(f) == pattern.charAt(f + m - g)) { f--; } suffixShift[i] = g - f; } } for (int i = 0; i < m; i++) { goodSuffix[i] = suffixShift[i] > m - i; } } public int search(String text, String pattern) { int n = text.length(); int m = pattern.length(); int i = 0; while (i <= n - m) { int j = m - 1; while (j >= 0 && pattern.charAt(j) == text.charAt(i + j)) { j--; } if (j < 0) { return i; // 匹配成功,返回匹配位置 } else { i += Math.max(goodSuffix[j + 1], j - badCharShift[text.charAt(i + j)]); } } return -1; // 未匹配成功,返回-1 } public static void main(String[] args) { BoyerMoore bm = new BoyerMoore(); String text = "This is a test"; String pattern = "test"; bm.preProcessPattern(pattern); int index = bm.search(text, pattern); if (index != -1) { System.out.println("Pattern found at index: " + index); } else { System.out.println("Pattern not found"); } } }
Summary:
This article introduces how to use Java language to implement the Boyer-Moore algorithm, and through specific code Examples demonstrate the use of the algorithm. The Boyer-Moore algorithm has high efficiency and wide application in the field of string matching. By rationally utilizing good suffix and bad character rules, the efficiency of string matching can be greatly improved. I hope this article will help you understand and practice the Boyer-Moore algorithm.
The above is the detailed content of How to implement Boyer-Moore algorithm using java. For more information, please follow other related articles on the PHP Chinese website!

Javadevelopmentisnotentirelyplatform-independentduetoseveralfactors.1)JVMvariationsaffectperformanceandbehavioracrossdifferentOS.2)NativelibrariesviaJNIintroduceplatform-specificissues.3)Filepathsandsystempropertiesdifferbetweenplatforms.4)GUIapplica

Java code will have performance differences when running on different platforms. 1) The implementation and optimization strategies of JVM are different, such as OracleJDK and OpenJDK. 2) The characteristics of the operating system, such as memory management and thread scheduling, will also affect performance. 3) Performance can be improved by selecting the appropriate JVM, adjusting JVM parameters and code optimization.

Java'splatformindependencehaslimitationsincludingperformanceoverhead,versioncompatibilityissues,challengeswithnativelibraryintegration,platform-specificfeatures,andJVMinstallation/maintenance.Thesefactorscomplicatethe"writeonce,runanywhere"

Platformindependenceallowsprogramstorunonanyplatformwithoutmodification,whilecross-platformdevelopmentrequiressomeplatform-specificadjustments.Platformindependence,exemplifiedbyJava,enablesuniversalexecutionbutmaycompromiseperformance.Cross-platformd

JITcompilationinJavaenhancesperformancewhilemaintainingplatformindependence.1)Itdynamicallytranslatesbytecodeintonativemachinecodeatruntime,optimizingfrequentlyusedcode.2)TheJVMremainsplatform-independent,allowingthesameJavaapplicationtorunondifferen

Javaispopularforcross-platformdesktopapplicationsduetoits"WriteOnce,RunAnywhere"philosophy.1)ItusesbytecodethatrunsonanyJVM-equippedplatform.2)LibrarieslikeSwingandJavaFXhelpcreatenative-lookingUIs.3)Itsextensivestandardlibrarysupportscompr

Reasons for writing platform-specific code in Java include access to specific operating system features, interacting with specific hardware, and optimizing performance. 1) Use JNA or JNI to access the Windows registry; 2) Interact with Linux-specific hardware drivers through JNI; 3) Use Metal to optimize gaming performance on macOS through JNI. Nevertheless, writing platform-specific code can affect the portability of the code, increase complexity, and potentially pose performance overhead and security risks.

Java will further enhance platform independence through cloud-native applications, multi-platform deployment and cross-language interoperability. 1) Cloud native applications will use GraalVM and Quarkus to increase startup speed. 2) Java will be extended to embedded devices, mobile devices and quantum computers. 3) Through GraalVM, Java will seamlessly integrate with languages such as Python and JavaScript to enhance cross-language interoperability.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft
