优先级队列

Posted 2022-06-13 area-h-p

优先级队列和普通队列并没有特大的不同之处，不一样的地方是，优先级队列的元素具有优先级之分。优先级高的元素在入队的时候应该放在队列前面。我下面实现的优先级队列元素的优先级由其数值大小决定。数值越小，优先级越高。ps:这和按一定规则排序好队列没啥区别啊。

实现如下

//header.h
#ifndef _HEADER_H
#define _HEADER_H
#include<iostream>
#include<assert.h>
#include<string.h>
using namespace std;
const int DefaultPQSize = 50;
template<class T>
class PQueue

    private:
        T *pqelements;
        int count;
        int maxSize;
        void adjust();
    public:
        PQueue(int sz = DefaultPQSize);
        ~PQueue()delete[]pqelements;
        bool Insert(const T& x);
        bool RemoveMin(T& x);//得到权值最大的元素，即取队头
        bool getFront(T& x) const;//得到权值最小的元素，也就是取队尾
        void makeEmpty();//置空数组
        bool IsEmpty() constreturn (this->count==0 ? true : false);
        bool IsFull() constreturn (this->maxSize==this->count ? true : false);void print() const;

;
template<class T>
void PQueue<T>::makeEmpty()

    //memset((void)*this->pqelements, ‘0‘, sizeof(T)*this->count);很奇怪为啥不让用memset，用了就出错。。
    for(int i=0; i<this->count; ++i)
        this->pqelements[i] = 0;
    this->count = 0;


template<class T>
bool PQueue<T>::getFront(T& x) const

    if(!this->IsEmpty())
    
        x = this->pqelements[this->count-1];
        return true;
    
    return false;


template<class T>
bool PQueue<T>::RemoveMin(T& x)

    if(!this->IsEmpty())
    
        x = this->pqelements[0];
        for(int i=0; i<this->count-1; ++i)
            this->pqelements[i] = this->pqelements[i+1];
        --this->count;
        return true;    
    
    return false;


template<class T>
PQueue<T>::PQueue(int sz):maxSize(sz), count(0)

    pqelements = new  T[maxSize];
    assert(pqelements != NULL);


template<class T>
bool PQueue<T>::Insert(const T& x)

    if(this->IsFull())
    
        T *newspace = new T[maxSize+DefaultPQSize];
        if(newspace == NULL)
            return false;
        this->maxSize = maxSize + DefaultPQSize;
        memcpy((void*)newspace, (void*)this->pqelements, sizeof(T)*this->count);
    
    this->pqelements[this->count++] = x;
    adjust();


template<class T>
void PQueue<T>::adjust()

    if(this->count==0)
        return;
    else
    
        for(int i=0; i<this->count-1; ++i)
            for(int j=i+1; j<this->count; ++j)
            
                if(this->pqelements[i]>this->pqelements[j])
                
                    this->pqelements[i] = this->pqelements[i] + this->pqelements[j];
                    this->pqelements[j] = this->pqelements[i] - this->pqelements[j];
                    this->pqelements[i] = this->pqelements[i] - this->pqelements[j];
                
            
    
    return;    

template<class T>
void PQueue<T>::print()const

    int i = 0;
    while(i!=this->count)
    
        cout<<this->pqelements[i++]<<"    ";
    
    cout<<endl;

#endif

 

#include"header.h"
int main()

    PQueue<int> pq;
    for(int i=0; i<100; ++i)//插入100个元素以检验是否可自动扩容
        pq.Insert(i);    
    pq.print();
    int i = 0;
    if(pq.getFront(i))
        cout<<i<<endl;

    
    if(pq.RemoveMin(i))
        pq.print();
    cout<<i<<endl;

    pq.makeEmpty();
    pq.print();
    return 0;

结果如下