/*

* Sample usage: java KMP DABRA AABRAACADABRAACAADABRA

*/

public class KMP {

private String pat;

private int[][] dfa;

public KMP(String pat){

// Build DFA from pattern.

this.pat = pat;

int M = pat.length();

int R = 256;

dfa = new int[R][M];

dfa[pat.charAt(0)][0] = 1;

for (int X=0, j=1; j<M; j++){

// Compute dfa[][j].

for (int c=0; c<R; c++)

dfa[c][j] = dfa[c][X]; // Copy mismatch cases

dfa[pat.charAt(j)][j] = j+1; // Set match case

X = dfa[pat.charAt(j)][X]; // Update restart state

}

}

public int search(String txt){

// Simulate operation of DFA on txt.

int i, j, N = txt.length(), M = pat.length();

for (i=0, j=0; i<N && j<M; i++)

j = dfa[txt.charAt(i)][j];

if (j==M) return i-M; // found (hit end of pattern)

else return N; // not found (hit end of text)

}

public static void main(String[] args){

String pat = args[0];

String txt = args[1];

KMP kmp = new KMP(pat);

StdOut.println("text: " + txt);

int offset = kmp.search(txt);

StdOut.print("pattern: ");

for (int i = 0; i<offset; i++)

StdOut.print(" ");

StdOut.println(pat);

}

}