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/** @author Prateek Kumar Oraon (https://github.com/prateekKrOraon) */
import java.util.Scanner;
// An implementaion of string matching using finite automata
public class StringMatchFiniteAutomata {
public static final int CHARS = 256;
public static int[][] FA;
public static Scanner scanner = null;
public static void main(String[] args) {
scanner = new Scanner(System.in);
System.out.println("Enter String");
String text = scanner.nextLine();
System.out.println("Enter pattern");
String pat = scanner.nextLine();
searchPat(text, pat);
scanner.close();
}
public static void searchPat(String text, String pat) {
int m = pat.length();
int n = text.length();
FA = new int[m + 1][CHARS];
computeFA(pat, m, FA);
int state = 0;
for (int i = 0; i < n; i++) {
state = FA[state][text.charAt(i)];
if (state == m) {
System.out.println("Pattern found at index " + (i - m + 1));
}
}
}
// Computes finite automata for the partern
public static void computeFA(String pat, int m, int[][] FA) {
for (int state = 0; state 0; ns--) {
if (pat.charAt(ns - 1) == x) {
for (int i = 0; i < ns - 1; i++) {
if (pat.charAt(i) != pat.charAt(state - ns + i + 1)) {
break;
}
if (i == ns - 1) {
return ns;
}
}
}
}
return 0;
}
}