package com.atguigu.kmp;
import java.util.Arrays;
public class KMPAlgorithm {
public static void main(String[] args) {
String str1 = "BBC ABCDAB ABCDABCDABDE";
String str2 = "ABCDABD";
int[] next = kmpNext("ABCDABD");
System.out.println("next=" + Arrays.toString(next));
int index = kmpSearch(str1, str2, next);
System.out.println("index=" + index);
}
public static int kmpSearch(String str1, String str2, int[] next) {
for(int i=0, j=0; i < str1.length();i++) {
while(j>0 && str1.charAt(i) != str2.charAt(j)) {
j = next[j-1];
}
if(str1.charAt(i)==str2.charAt(j)) {
j++;
}
if(j == str2.length()) {
return i-j+1;
}
}
return -1;
}
public static int[] kmpNext(String dest) {
int[] next = new int[dest.length()];
next[0] = 0;
for(int i = 1,j = 0; i < dest.length();i++) {
while(j > 0 && dest.charAt(i) != dest.charAt(j)) {
j = next[j-1];
}
if(dest.charAt(i) == dest.charAt(j)) {
j++;
}
next[i] = j;
}
return next;
}
}