KMP算法----java实现

字符串的模式匹配本文先实现最基本的回溯实现的已经KMP算法，BM算法后面博文继续实现。ps:本篇博文强烈参考了July大神的作品，地址http://blog.csdn.net/v_july_v/article/details/6545192.再次感激大神~~

1.最基本的回溯实现字符串模式匹配

package com.sheepmu;public class KMPText {public static void main(String[] args){String s0="abcdeabckkfgh";String s1="abck";char[] as0=s0.toCharArray();char[] as1=s1.toCharArray();System.out.println(getIndex(as0,as1));}public static int getIndex(char[] as0,char[] as1){int len0=as0.length;int len1=as1.length;int i=0,j=0;while(i<len0&&j<len1){if(as0[i]==as1[j]){i++;j++;}else{i=i-j+1;j=0;}}if(j>=len1){return i-j;}return -1;}}

2.KMP算法实现字符串模式匹配

package com.sheepmu;public class KMPText {public static void main(String[] args){String s0="abcdeabckkfgh";String s1="abcke";char[] as0=s0.toCharArray();char[] as1=s1.toCharArray();System.out.println(getKMP(as0,as1));}public static int[] next(char[] as1){int[] next=new int[as1.length];next[0]=-1;int len1=as1.length;int i=0,j=-1;while(i<len1-1)//!!!!!!!!!!!!!记得-1{if(j==-1||as1[i]==as1[j]){i++;j++;if(as1[i]!=as1[j]){next[i]=j;}else{next[i]=next[j];}}else{j=next[j];}}return next;}public static int getKMP(char[] as0,char[] as1){ int len0=as0.length;int len1=as1.length;int i=0,j=0;int[] next=next(as1);while(i<len0&&j<len1){if(j==-1||as0[i]==as1[j]){i++;j++;}else{j=next[j];}}if(j>=len1){return i-j;}return -1;}}