heap.java

利用霍夫曼树实现文本压缩。如果是文本可以压缩到40％的大小

package org.galaxy_OPEN.www.datastructures.huffman;

public class Heap {
	private Node[] heapArray;

	private int maxSize;

	private int currentSize;

	public Heap(int mx) {
		maxSize = mx;
		currentSize = 0;
		heapArray = new Node[maxSize];
	}

	public int getCurrentSize() {
		return currentSize;
	}

	public Node remove() {
		Node root = heapArray[0];
		heapArray[0] = heapArray[--currentSize];
		trickleDown(0);
		return root;
	}

	public void trickleDown(int index) {
		int smallerChild;
		Node top = heapArray[index];
		while (index < currentSize / 2) {
			int leftChild = 2 * index + 1;
			int rightChild = leftChild + 1;
			if (rightChild < currentSize
					&& heapArray[leftChild].getFrequency() > heapArray[rightChild]
							.getFrequency())
				smallerChild = rightChild;
			else
				smallerChild = leftChild;
			if (top.getFrequency() < heapArray[smallerChild].getFrequency())
				break;
			heapArray[index] = heapArray[smallerChild];
			index = smallerChild;
		}
		heapArray[index] = top;
	}

	public void trickleUp(int index) {
		int parent = (index - 1) / 2;
		Node temp = heapArray[index];

		while (index > 0
				&& heapArray[parent].getFrequency() > temp.getFrequency()) {
			heapArray[index] = heapArray[parent];
			index = parent;
			parent = (parent - 1) / 2;
		}

		heapArray[index] = temp;
	}

	public void append(Node newNode) {
		if (currentSize < maxSize)
			heapArray[currentSize++] = newNode;
	}

	public void insertOrdered(Node newNode) {
		append(newNode);
		trickleUp(currentSize - 1);
	}

	public void sort() {
		for (int j = currentSize / 2 - 1; j >= 0; j--)
			trickleDown(j);
	}
}