二叉樹（四）二叉堆

二叉堆（也可作為簡單的優先隊列）的建立、增、刪、自調整。

main.cpp：

#include <iostream>
#include "BinaryHeap.h"
using namespace std;

int main()
{
    BinaryHeap<int> bh(BinaryHeap<int>::HeapType::MINIMEM);

    auto il = { 5,1,7,4,8,9 };
    bh.push(il.begin(), il.end());
    bh.show();
    cout << endl;
    cout << "Pop head: " << bh.head() << endl;
    bh.pop();
    bh.show();
    cout << endl;

    return 0;
}

BinaryHeap.h：

#pragma once
#ifndef __BINARYHEAP_H__
#define __BINARYHEAP_H__


template<typename _Ty>
class BinaryHeap
{
public:
    enum class HeapType :bool { MINIMEM = 0, MAXIMEM };

public:
    BinaryHeap() = default;
    BinaryHeap(HeapType _heapType) { heapType = _heapType; }
    ~BinaryHeap() { delete[] heapArr; heapArr = nullptr; }
    bool empty() const { return size_n == 0; }
    size_t size() { return size_n; }

    template<typename _Iter>
    void push(_Iter, _Iter);
    void push(const _Ty&);
    void pop();
    void swap();
    _Ty& head() const;
    void show() const;

    _Ty& operator [] (int);

private:
    bool compare(const _Ty& _a, const _Ty& _b)
    {
        return (heapType == HeapType::MAXIMEM) ? (_a > _b) : (_a < _b);
    }

private:
    size_t size_n = 0;
    size_t MaxSize = 0;
    _Ty* heapArr = nullptr;
    HeapType heapType = HeapType::MAXIMEM;
};

template<typename _Ty>
template<typename _Iter>
void BinaryHeap<_Ty>::push(_Iter _it1, _Iter _it2)
{
    while (_it1 != _it2)
    {
        push(*_it1);
        ++_it1;
    }
}

template<typename _Ty>
void BinaryHeap<_Ty>::push(const _Ty& _val)
{
    ++size_n;
    if (heapArr == nullptr)
    {
        MaxSize = 10;
        heapArr = new _Ty[MaxSize];
    }
    else if (MaxSize - size_n < 0)
    {
        MaxSize << 2;
        _Ty* tempArr = new _Ty[MaxSize];
        for (size_t it = 0; it < size_n - 1; ++it)
            tempArr[it] = heapArr[it];
        delete[] heapArr;
        heapArr = tempArr;
        tempArr = nullptr;
    }
    heapArr[size_n - 1] = _val;
    size_t childInex = size_n - 1;
    while (childInex > 0)
    {
        if (compare(_val, heapArr[(childInex - 1) / 2]))
        {
            heapArr[childInex] = heapArr[(childInex - 1) / 2];
            childInex = (childInex - 1) / 2;
        }
        else
            break;
    }
    heapArr[childInex] = _val;
}

template<typename _Ty>
void BinaryHeap<_Ty>::pop()
{
    if (size_n == 0) return;
    --size_n;
    heapArr[0] = heapArr[size_n];
    size_t childInex = 1;
    _Ty temp = heapArr[0];
    while (childInex < size_n)
    {
        if (childInex + 1 < size_n && compare(heapArr[childInex + 1], heapArr[childInex]))
            ++childInex;
        if (compare(temp, heapArr[childInex]))
            break;
        heapArr[(childInex - 1) / 2] = heapArr[childInex];
        childInex = 2 * childInex + 1;
    }
    heapArr[(childInex - 1) / 2] = temp;
}

template<typename _Ty>
void BinaryHeap<_Ty>::swap()
{
    std::swap(size_n);
    std::swap(MaxSize);
    std::swap(heapArr);
    std::swap(heapType);
}

template<typename _Ty>
_Ty& BinaryHeap<_Ty>::head() const
{
    if (heapArr == nullptr || size_n < 1)
        throw std::exception("Heap is empty.");
    return heapArr[0];
}

template<typename _Ty>
void BinaryHeap<_Ty>::show() const
{
    for (size_t i = 0; i < size_n; ++i)
        std::cout << heapArr[i] << " ";
}

template<typename _Ty>
_Ty& BinaryHeap<_Ty>::operator [] (int _index)
{
    if (_index >= size_n) throw std::exception("Index out of range.");
    return heapArr[_index];
}


#endif // !__BINARYHEAP_H__