/**
 * Sorts an array from lo to hi by building successive heap structures.
 *
 * An array A[lo:hi] is said to satisfy the "heap property" if for i = 0,
 * 1, .., hi - lo:
 *   A[lo + i] <= A[lo + 2 * i + 1]  and
 *   A[lo + i] < = A[lo + 2 * i + 2], whenever these indices are
 *     in the range lo..hi.
 *
 * Heapsort is part of the hard-split/easy-join family,
 * since all of the work is done in the split phase.
 *
 * Copyright 2000 - Dung X. Nguyen - All rights reserved.
 */
public class HeapSorter extends ASorter
{
    /**
     * Heapifies A from lo to hi.
     * @param A an array of int.
     * @param lo the lo index of A.
     * @param hi
     */
    public HeapSorter(int[] A, int lo, int hi)
    {
	for (int cur = (hi - lo + 1) / 2; cur >= lo; cur--) {
	    Heapifier.Singleton.siftDown(A, lo, cur, hi);
	}
    }

    /**
     * Swaps A[lo] with A[hi] and sift A[lo] down to hi - 1.
     * Assumes A satisfies the heap property.
     * @return hi
     */
    public int split(int[] A, int lo, int hi)
    {
	int temp = A[hi];
	A[hi] = A[lo];
	A[lo] = temp;
	Heapifier.Singleton.siftDown(A, lo, lo, hi - 1);
	return hi;
    }

    /**
     * Does nothing, assuming s == hi.
     */
    public void join(int[] A, int lo, int s, int hi)
    {
    }

    public static void main(String[] args)
    {
	//int[] A =  {};
	//int[] A =  {50};
	//int[] A =  {50, 80};
	//int[] A =  {80, 50};
	//int[] A =  {50, 80, 20};
	//int[] A =  {80, 50, 20};
	int[] A = {999, 50, 80, 20, 60, 90, 40, 30, 70, 10, -999};
	int arrayLen = A.length;
	System.out.println("A =");
	for (int i = 0; i < arrayLen; i++) {
	    System.out.print(A[i] + "  ");
	}
	int lo = 1;
	int hi = arrayLen - 2;
	System.out.println("\nHeapifying A[" + lo + "..." + hi + "]");

	// Only a part of A is to be heapified.

	ASorter sorter = new HeapSorter(A, lo, hi);
	System.out.println("\nHeapified A =");
	for (int i = 0; i < A.length; i++) {
	    System.out.print(A[i] + "  ");
	}
	System.out.println("\nSorting A[" + lo + "..." + hi + "]");
	sorter.sort(A, lo, hi);		// Only a part of A is to be sorted.
	System.out.println("Sorted A =");
	for (int i = 0; i < A.length; i++) {
	    System.out.print(A[i] + "  ");
	}
	System.out.println("\nDone");
    }
}