package edu.princeton.cs.algs4;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* Compilation: javac Knuth.java
* Execution: java Knuth < list.txt
* Dependencies: StdIn.java StdOut.java
* Data files: http://algs4.cs.princeton.edu/11model/cards.txt
* http://algs4.cs.princeton.edu/11model/cardsUnicode.txt
*
* Reads in a list of strings and prints them in random order.
* The Knuth (or Fisher-Yates) shuffling algorithm guarantees
* to rearrange the elements in uniformly random order, under
* the assumption that Math.random() generates independent and
* uniformly distributed numbers between 0 and 1.
*
* % more cards.txt
* 2C 3C 4C 5C 6C 7C 8C 9C 10C JC QC KC AC
* 2D 3D 4D 5D 6D 7D 8D 9D 10D JD QD KD AD
* 2H 3H 4H 5H 6H 7H 8H 9H 10H JH QH KH AH
* 2S 3S 4S 5S 6S 7S 8S 9S 10S JS QS KS AS
*
* % java Knuth < cards.txt
* 6H
* 9C
* 8H
* 7C
* JS
* ...
* KH
*
* % more cardsUnicode.txt
* 2♣ 3♣ 4♣ 5♣ 6♣ 7♣ 8♣ 9♣ 10♣ J♣ Q♣ K♣ A♣
* 2♦ 3♦ 4♦ 5♦ 6♦ 7♦ 8♦ 9♦ 10♦ J♦ Q♦ K♦ A♦
* 2♥ 3♥ 4♥ 5♥ 6♥ 7♥ 8♥ 9♥ 10♥ J♥ Q♥ K♥ A♥
* 2♠ 3♠ 4♠ 5♠ 6♠ 7♠ 8♠ 9♠ 10♠ J♠ Q♠ K♠ A♠
*
* % java Knuth < cardsUnicode.txt
* 2♠
* K♥
* 6♥
* 5♣
* J♣
* ...
* A♦
*
*************************************************************************/
/**
* The <tt>Knuth</tt> class provides a client for reading in a
* sequence of strings and <em>shuffling</em> them using the Knuth (or Fisher-Yates)
* shuffling algorithm. This algorithm guarantees to rearrange the
* elements in uniformly random order, under
* the assumption that Math.random() generates independent and
* uniformly distributed numbers between 0 and 1.
* <p>
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/11model">Section 1.1</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class Knuth {
// this class should not be instantiated
private Knuth() { }
/**
* Rearranges an array of objects in uniformly random order
* (under the assumption that <tt>Math.random()</tt> generates independent
* and uniformly distributed numbers between 0 and 1).
* @param a the array to be shuffled
* @see StdRandom
*/
public static void shuffle(Object[] a) {
int N = a.length;
for (int i = 0; i < N; i++) {
// choose index uniformly in [i, N-1]
int r = i + (int) (Math.random() * (N - i));
Object swap = a[r];
a[r] = a[i];
a[i] = swap;
}
}
/**
* Reads in a sequence of strings from standard input, shuffles
* them, and prints out the results.
*/
public static void main(String[] args) {
// read in the data
String[] a = StdIn.readAllStrings();
// shuffle the array
Knuth.shuffle(a);
// print results.
for (int i = 0; i < a.length; i++)
StdOut.println(a[i]);
}
}
/*************************************************************************
* Copyright 2002-2012, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4-package.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-package.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-package.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-package.jar. If not, see http://www.gnu.org/licenses.
*************************************************************************/