com.liferay.portal.kernel.util.KMPSearch Maven / Gradle / Ivy
/**
* Copyright (c) 2000-2013 Liferay, Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or modify it under
* the terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 2.1 of the License, or (at your option)
* any later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
* details.
*/
package com.liferay.portal.kernel.util;
/**
*
* See http://en.wikipedia.org/wiki/Knuth-Morris-Pratt_algorithm.
*
*
* @author Shuyang Zhou
*/
public class KMPSearch {
public static int[] generateNexts(byte[] pattern) {
int length = pattern.length;
int[] nexts = new int[length];
nexts[0] = -1;
int i = 0;
int j = -1;
while (i < (length - 1)) {
if ((j == -1) || (pattern[i] == pattern[j])) {
i++;
j++;
nexts[i] = j;
}
else {
j = nexts[j];
}
}
return nexts;
}
public static int[] generateNexts(char[] pattern) {
int length = pattern.length;
int[] nexts = new int[length];
nexts[0] = -1;
int i = 0;
int j = -1;
while (i < (length - 1)) {
if ((j == -1) || (pattern[i] == pattern[j])) {
i++;
j++;
nexts[i] = j;
}
else {
j = nexts[j];
}
}
return nexts;
}
public static int[] generateNexts(CharSequence pattern) {
int length = pattern.length();
int[] nexts = new int[length];
nexts[0] = -1;
int i = 0;
int j = -1;
while (i < (length - 1)) {
if ((j == -1) || (pattern.charAt(i) == pattern.charAt(j))) {
i++;
j++;
nexts[i] = j;
}
else {
j = nexts[j];
}
}
return nexts;
}
public static int search(byte[] text, byte[] pattern) {
int[] nexts = generateNexts(pattern);
return search(text, 0, text.length, pattern, nexts);
}
public static int search(byte[] text, byte[] pattern, int[] nexts) {
return search(text, 0, text.length, pattern, nexts);
}
public static int search(
byte[] text, int offset, byte[] pattern, int[] nexts) {
return search(text, offset, text.length - offset, pattern, nexts);
}
public static int search(
byte[] text, int offset, int length, byte[] pattern, int[] nexts) {
int patternLength = pattern.length;
int i = 0;
int j = 0;
while ((i < length) && (j < patternLength)) {
if ((j == -1) || (text[i + offset] == pattern[j])) {
i++;
j++;
}
else {
j = nexts[j];
}
}
if (j >= patternLength) {
return i - patternLength + offset;
}
else {
return -1;
}
}
public static int search(char[] text, char[] pattern) {
int[] nexts = generateNexts(pattern);
return search(text, 0, text.length, pattern, nexts);
}
public static int search(char[] text, char[] pattern, int[] nexts) {
return search(text, 0, text.length, pattern, nexts);
}
public static int search(
char[] text, int offset, char[] pattern, int[] nexts) {
return search(text, offset, text.length - offset, pattern, nexts);
}
public static int search(
char[] text, int offset, int length, char[] pattern, int[] nexts) {
int patternLength = pattern.length;
int i = 0;
int j = 0;
while ((i < length) && (j < patternLength)) {
if ((j == -1) || (text[i + offset] == pattern[j])) {
i++;
j++;
}
else {
j = nexts[j];
}
}
if (j >= patternLength) {
return i - patternLength + offset;
}
else {
return -1;
}
}
public static int search(CharSequence text, CharSequence pattern) {
int[] nexts = generateNexts(pattern);
return search(text, 0, text.length(), pattern, nexts);
}
public static int search(
CharSequence text, CharSequence pattern, int[] nexts) {
return search(text, 0, text.length(), pattern, nexts);
}
public static int search(
CharSequence text, int offset, CharSequence pattern, int[] nexts) {
return search(text, offset, text.length() - offset, pattern, nexts);
}
public static int search(
CharSequence text, int offset, int length, CharSequence pattern,
int[] nexts) {
int patternLength = pattern.length();
int i = 0;
int j = 0;
while ((i < length) && (j < patternLength)) {
if (j == -1) {
i++;
j++;
}
else {
char c1 = text.charAt(i + offset);
char c2 = pattern.charAt(j);
if ((c1 == c2) || (c1 == Character.toUpperCase(c2))) {
i++;
j++;
}
else {
j = nexts[j];
}
}
}
if (j >= patternLength) {
return i - patternLength + offset;
}
else {
return -1;
}
}
}