#### String Match Finite Automata

a
A
```package com.thealgorithms.others;

/**
* @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 <= m; ++state) {
for (int x = 0; x < CHARS; ++x) {
FA[state][x] = getNextState(pat, m, state, x);
}
}
}

public static int getNextState(String pat, int m, int state, int x) {
// if current state is less than length of pattern
// and input character of pattern matches the character in the alphabet
// then automata goes to next state
if (state < m && x == pat.charAt(state)) {
return state + 1;
}

for (int ns = state; ns > 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;
}
}
```