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/******************************************************************************
* Compilation: javac Heap.java
* Execution: java Heap < input.txt
* Dependencies: StdOut.java StdIn.java
* Data files: https://algs4.cs.princeton.edu/24pq/tiny.txt
* https://algs4.cs.princeton.edu/24pq/words3.txt
*
* Sorts a sequence of strings from standard input using heapsort.
*
* % more tiny.txt
* S O R T E X A M P L E
*
* % java Heap < tiny.txt
* A E E L M O P R S T X [ one string per line ]
*
* % more words3.txt
* bed bug dad yes zoo ... all bad yet
*
* % java Heap < words3.txt
* all bad bed bug dad ... yes yet zoo [ one string per line ]
*
******************************************************************************/
package edu.princeton.cs.algs4;
/**
* The {@code Heap} class provides a static methods for heapsorting
* an array.
*
* For additional documentation, see Section 2.4 of
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class Heap {
// This class should not be instantiated.
private Heap() { }
/**
* Rearranges the array in ascending order, using the natural order.
* @param pq the array to be sorted
*/
public static void sort(Comparable[] pq) {
int n = pq.length;
for (int k = n/2; k >= 1; k--)
sink(pq, k, n);
while (n > 1) {
exch(pq, 1, n--);
sink(pq, 1, n);
}
}
/***************************************************************************
* Helper functions to restore the heap invariant.
***************************************************************************/
private static void sink(Comparable[] pq, int k, int n) {
while (2*k <= n) {
int j = 2*k;
if (j < n && less(pq, j, j+1)) j++;
if (!less(pq, k, j)) break;
exch(pq, k, j);
k = j;
}
}
/***************************************************************************
* Helper functions for comparisons and swaps.
* Indices are "off-by-one" to support 1-based indexing.
***************************************************************************/
private static boolean less(Comparable[] pq, int i, int j) {
return pq[i-1].compareTo(pq[j-1]) < 0;
}
private static void exch(Object[] pq, int i, int j) {
Object swap = pq[i-1];
pq[i-1] = pq[j-1];
pq[j-1] = swap;
}
// print array to standard output
private static void show(Comparable[] a) {
for (int i = 0; i < a.length; i++) {
StdOut.println(a[i]);
}
}
/**
* Reads in a sequence of strings from standard input; heapsorts them;
* and prints them to standard output in ascending order.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
String[] a = StdIn.readAllStrings();
Heap.sort(a);
show(a);
}
}
/******************************************************************************
* 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.
******************************************************************************/