KMP算法

字符串的快速匹配
 1 package cn.wubowei;
 2 
 3 public class KMP {
 4 
 5     public static void main(String[] args) {
 6         // TODO Auto-generated method stub
 7          String pattern="ABABCABAA";
 8          char[] patternch=pattern.toCharArray();
 9          char[] text="ABABABABCABAAABAB".toCharArray();
10          int n= pattern.length();
11          int[] prefix=new int[n];
12 //         prefixtable(patternch, prefix, n);
13 //         movePrefixTable(prefix, n);
14          kmpsearch(text, patternch);
15          
16     }
17     public  static void prefixtable (char pattern[], int prefix[], int n) {
18         prefix[0]=0;
19         int len=0;
20         int i=1;
21         while (i<n) {
22             if(pattern[i] == pattern[len]) {
23                 len++;
24                 prefix[i]=len;
25                 i++;
26             }else {
27                 if(len>0) {
28                 len =prefix[len-1];
29                 }else {
30                     prefix[i]= len;
31                     i++;
32                 }
33             }
34         }
35     }
36     
37     public static void movePrefixTable(int prefix[], int n) {
38 //        int i=0;
39         for(int i=n-1;i>0;i--) {
40             prefix[i]=prefix[i-1];
41         }
42         prefix[0]=-1;
43     }
44     
45     public static void kmpsearch (char text[], char pattern[]) {
46         int n= pattern.length;
47         int m=text.length;
48         int[] prefix=new int[n];
49         prefixtable(pattern, prefix, n);
50         movePrefixTable(prefix,n);
51         int i=0;
52         int j=0;
53     
54         while(i<m) {
55             if(j==n-1&&text[i]==pattern[j]) {
56                 System.out.println(i-j);
57                 j=prefix[j];
58             }
59             if(text[i]== pattern[j]) {
60                 i++;
61                 j++;
62             }else {
63                 j=prefix[j];
64                 if(j==-1) {
65                     i++;j++;
66                 }
67                     
68             }
69         }
70     }
71     
72 }