Java 實現最大堆__Java

最大堆的特點是父元素比子項目大，並且是一棵完全二叉樹。

堆介面：

/** * Create by zxb on 2017/9/10 */public interface IHeap<T extends Comparable<T>> {    void display();    void initOriginList(List<T> orginList);    void makeHeap(int first, int last);    void popHeap(int first, int last);    void pushHeap(int first, int last);    List<T> getHeap();}

堆實現，這裡採用的是動態數組來做儲存

/** * Create by zxb on 2017/9/10 */public class HeapImpl<T extends Comparable<T>> implements IHeap<T> {    private List<T> heap;    private List<T> orginList;    public void initOriginList(List<T> orginList) {        this.orginList = orginList;    }    public List<T> getHeap() {        return heap;    }    public HeapImpl() {        this.heap = new ArrayList<>();    }    /**     * 插入對應上浮     *     * @param start     */    protected void adjustUp(int start) {        int currentIndex = start;        int parentIndex = (currentIndex - 1) / 2;        T tmp = heap.get(currentIndex);        while (currentIndex > 0) {            int cmp = heap.get(parentIndex).compareTo(tmp);            if (cmp >= 0) {                break;            } else {                heap.set(currentIndex, heap.get(parentIndex));                currentIndex = parentIndex;                parentIndex = (parentIndex - 1) / 2;            }        }        heap.set(currentIndex, tmp);    }    public void insert(T data) {        int size = heap.size();        heap.add(data);    // 將"數組"插在表尾        adjustUp(size);        // 向上調整堆    }    public void remove(int index) {        int size = heap.size();        heap.set(index, heap.get(size - 1));        heap.remove(size - 1);        adjustDown(index);    }    /**     * 刪除對應下沉     *     * @param index     */    private void adjustDown(int index) {        int currentIndex = index;        int leftChildIndex = index * 2 + 1;        int rightChildIndex = index * 2 + 2;        T tmp = heap.get(currentIndex);        int size = heap.size();        while (leftChildIndex < size) {            T left = null;            T right = null;            if (leftChildIndex < size) {                left = heap.get(leftChildIndex);            }            if (rightChildIndex < size) {                right = heap.get(rightChildIndex);            }            int maxIndex = right == null ? leftChildIndex : (left.compareTo(right) >= 0 ? leftChildIndex : rightChildIndex);            T max = heap.get(maxIndex);            if(tmp.compareTo(max)>=0){                break;            }else{                heap.set(currentIndex, max);                heap.set(maxIndex, tmp);                leftChildIndex = maxIndex * 2 +1;                rightChildIndex = maxIndex +1;            }        }    }    public void makeHeap(int first, int last) {        for (int i = first; i < last; i++) {            insert(orginList.get(i));        }    }    public void popHeap(int first, int last) {        remove(first);    }    public void pushHeap(int first, int last) {        adjustUp(last - 1);    }    public void display() {        System.out.println(heap);    }    public static void main(String[] args) {        IHeap<Integer> heap = new HeapImpl<>();        heap.initOriginList(Arrays.asList(10, 20, 30, 5, 15));        System.out.println("初始構建堆：");        heap.makeHeap(0, 5);        heap.display();        System.out.println("彈出堆頂：");        heap.popHeap(0, 5);        heap.display();        System.out.println("彈出堆頂：");        heap.popHeap(0, 4);        heap.display();        System.out.println("插入堆尾：");        heap.getHeap().add(90);        heap.display();        System.out.println("重新排列：");        heap.pushHeap(0, 4);        heap.display();    }}

運行結果：