edu.princeton.cs.algs4.GREP Maven / Gradle / Ivy
/******************************************************************************
* Compilation: javac GREP.java
* Execution: java GREP regexp < input.txt
* Dependencies: NFA.java StdOut.java
* Data files: https://algs4.cs.princeton.edu/54regexp/tinyL.txt
*
* This program takes an RE as a command-line argument and prints
* the lines from standard input having some substring that
* is in the language described by the RE.
*
* % more tinyL.txt
* AC
* AD
* AAA
* ABD
* ADD
* BCD
* ABCCBD
* BABAAA
* BABBAAA
*
* % java GREP "(A*B|AC)D" < tinyL.txt
* ABD
* ABCCBD
*
******************************************************************************/
package edu.princeton.cs.algs4;
/**
* The {@code GREP} class provides a client for reading in a sequence of
* lines from standard input and printing to standard output those lines
* that contain a substring matching a specified regular expression.
*
* For additional documentation, see Section 3.1 of
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class GREP {
// do not instantiate
private GREP() { }
/**
* Interprets the command-line argument as a regular expression
* (supporting closure, binary or, parentheses, and wildcard)
* reads in lines from standard input; writes to standard output
* those lines that contain a substring matching the regular
* expression.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
String regexp = "(.*" + args[0] + ".*)";
NFA nfa = new NFA(regexp);
while (StdIn.hasNextLine()) {
String line = StdIn.readLine();
if (nfa.recognizes(line)) {
StdOut.println(line);
}
}
}
}
/******************************************************************************
* Copyright 2002-2018, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4.jar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* algs4.jar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with algs4.jar. If not, see http://www.gnu.org/licenses.
******************************************************************************/