数据结构与算法--堆

 最小堆C++实现：（可以插入一个数、删除最小值）

#include <iostream>
using namespace std;

const int DefaultSize = 1000005;

template<class T>
class MinHeap{
    T* heap;
    int currentSize;
    int maxHeapSize;
    void siftDown(int start);
    void siftUp(int start);

public:
    MinHeap(int sz=DefaultSize);
    MinHeap(T arr[], int n);
    ~MinHeap(){delete[] heap;}
    bool Insert(const T& x);
    bool Remove();
    void Print();
    T get_min() const {if(currentSize!=0) return heap[0]; return 0;}
    bool IsEmpty() const {return currentSize==0;}
    bool IsFull() const {return currentSize==maxHeapSize;}
    int get_maxHeapSize() const {return maxHeapSize;}
    int get_currentSize() const {return currentSize;}
};

template<class T>
MinHeap<T>::MinHeap(int sz){
    if(sz<DefaultSize) sz=DefaultSize;
    heap = new T[sz];
    currentSize = 0;
    maxHeapSize = sz;
}

template<class T>
MinHeap<T>::MinHeap(T arr[], int n){
    int sz = n*2;
    if(sz<DefaultSize) sz=DefaultSize;
    heap = new T[sz];
    for(int i=0;i<n;i++) heap[i] = arr[i];
    currentSize = n;
    maxHeapSize = sz;
    int start = (currentSize-1-1)/2;
    while(start>=0){
        siftDown(start);
        start--;
    }
}

template<class T>
void MinHeap<T>::siftDown(int start){
    int i=start, j=i*2+1;
    int temp=heap[i];
    while(j<=currentSize-1){
        if(j+1<=currentSize-1&&heap[j+1]<heap[j]) j++;
        if(temp<=heap[j]) break;
        heap[i]=heap[j];
        i=j;
        j=i*2+1;
    }
    heap[i]=temp;
}

template<class T>
void MinHeap<T>::siftUp(int start){
    int j=start, i=(j-1)/2;
    int temp=heap[j];
    while(j>0){
        if(heap[i]<=temp) break;
        heap[j]=heap[i];
        j=i;
        i=(j-1)/2;
    }
    heap[j]=temp;
}

template<class T>
void MinHeap<T>::Print(){
    for(int i=0;i<currentSize;i++){
        cout<<heap[i]<<" ";
    }
    cout<<endl;
}

template<class T>
bool MinHeap<T>::Insert(const T& x){
    if(currentSize==maxHeapSize){
        cerr<<"Heap Full"<<endl;
        return false;
    }
    heap[currentSize] = x;
    siftUp(currentSize);
    currentSize++;
    return true;
}

template<class T>
bool MinHeap<T>::Remove(){
    if(currentSize==0){
        cerr<<"Heap Empty"<<endl;
        return false;
    }
    heap[0]=heap[currentSize-1];
    currentSize--;
    siftDown(0);
    return true;
}

int main()
{
    MinHeap<int> hp;
    int n;cin>>n;
    for(int i=1;i<=n;i++){
        int op;cin>>op;
        if(op==1){
            int num;cin>>num;
            hp.Insert(num);
        }
        else if(op==2){
            cout<<hp.get_min()<<endl;
        }
        else{
            hp.Remove();
        }
    }
    return 0;
}

堆可以维护一组数中的最大值/最小值

参考：

最小堆c++实现_c++手写最小堆_Andy Dennis的博客-CSDN博客