TopM.java
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/******************************************************************************
* Compilation: javac TopM.java
* Execution: java TopM m < input.txt
* Dependencies: MinPQ.java Transaction.java StdIn.java StdOut.java
* Data files: http://algs4.cs.princeton.edu/24pq/tinyBatch.txt
*
* Given an integer m from the command line and an input stream where
* each line contains a String and a long value, this MinPQ client
* prints the m lines whose numbers are the highest.
*
* % java TopM 5 < tinyBatch.txt
* Thompson 2/27/2000 4747.08
* vonNeumann 2/12/1994 4732.35
* vonNeumann 1/11/1999 4409.74
* Hoare 8/18/1992 4381.21
* vonNeumann 3/26/2002 4121.85
*
******************************************************************************/
package edu.princeton.cs.algs4;
/**
* The {@code TopM} class provides a client that reads a sequence of
* transactions from standard input and prints the <em>m</em> largest ones
* to standard output. This implementation uses a {@link MinPQ} of size
* at most <em>m</em> + 1 to identify the <em>M</em> largest transactions
* and a {@link Stack} to output them in the proper order.
* <p>
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/24pq">Section 2.4</a>
* of <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class TopM {
// This class should not be instantiated.
private TopM() { }
/**
* Reads a sequence of transactions from standard input; takes a
* command-line integer m; prints to standard output the m largest
* transactions in descending order.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
int m = Integer.parseInt(args[0]);
MinPQ<Transaction> pq = new MinPQ<Transaction>(m+1);
while (StdIn.hasNextLine()) {
// Create an entry from the next line and put on the PQ.
String line = StdIn.readLine();
Transaction transaction = new Transaction(line);
pq.insert(transaction);
// remove minimum if m+1 entries on the PQ
if (pq.size() > m)
pq.delMin();
} // top m entries are on the PQ
// print entries on PQ in reverse order
Stack<Transaction> stack = new Stack<Transaction>();
for (Transaction transaction : pq)
stack.push(transaction);
for (Transaction transaction : stack)
StdOut.println(transaction);
}
}
/******************************************************************************
* Copyright 2002-2016, 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.
******************************************************************************/