MinHeap.java

package org.oscim.utils;

public class MinHeap {
	private int[] data;
	private float[] heap;

	public static final class Item {
		public int pos;
		public float prio;
		public int index;
	}

	int size;

	private final Item it = new Item();

	public MinHeap(float[] heap, int[] data) {
		this.heap = heap;
		this.data = data;
		size = 1;
	}

	public void push(float prio, int d) {
		int idx = size++;
		int n = idx >> 1;
		while (idx > 1 && heap[n] > prio) {
			heap[idx] = heap[n];
			data[idx] = data[n];
			idx = n;
			n >>= 1;
		}

		heap[idx] = prio;
		data[idx] = d;
	}

	public Item pop() {
		if (size == 1)
			return null;

		it.pos = data[1];
		it.prio = heap[1];

		int idx = --size;

		if (idx > 1) {
			heap[1] = heap[idx];
			data[1] = data[idx];
			heapify();
		}
		return it;
	}

	public int peek() {
		return data[1];
	}

	private void heapify() {
		float root = heap[1];
		int tmp = data[1];

		int last = size;
		int idx = 1;

		while (true) {
			// left child
			int c = idx << 1;
			if (c > last)
				break;
			// right child
			if (c + 1 <= last && heap[c + 1] < heap[c])
				c++;

			float val = heap[c];
			if (val >= root)
				break;

			heap[idx] = val;
			data[idx] = data[c];
			idx = c;
		}

		heap[idx] = root;
		data[idx] = tmp;
	}

	public static void main(String[] args) {
		MinHeap h = new MinHeap(new float[10], new int[10]);
		h.push(10, 10);
		h.push(12, 12);
		h.push(21, 21);
		h.push(31, 31);
		h.push(14, 14);
		h.push(2, 2);
		Item it;
		for (int i = 0; i < 10; i++) {

			it = h.pop();
			if (it != null)
				System.out.println(it.pos + " " + it.prio);
		}

	}
}