练习8——队列

1、队列的抽象类，虚函数，纯虚函数。

class Queue{
public:
    Queue(){};
    ~Queue(){};
    virtual int EnQueue(int x)=0;
    virtual int DeQueue(int &x)=0;
    virtual int getFront(int &x)=0;
    virtual int IsEmpty()const=0;
    virtual int IsFull()const=0;
};

2、循环队列

#include <iostream>
#include <assert.h>
using namespace std;
class SeqQueue{
protected:
    int rear,front;
    int *elements;
    int maxSize;
public:
    SeqQueue(int sz=10);
    ~SeqQueue(){delete[] elements;}
    int EnQueue(int &x);
    int DeQueue(int &x);
    int getFront(int &x);
    void makeEmpty(){front=rear=0;}
    int IsEmpty()const {return front==rear;}
    int IsFull()const{
        return ((rear+1)%maxSize==front);
    }
    int getSize()const{
        return (rear-front+maxSize)%maxSize;
    }
    void output();
};
SeqQueue::SeqQueue(int sz) {
    front=rear=0;
    maxSize=sz;
    elements=new int[maxSize];
    assert(elements!=NULL);
}
int SeqQueue::EnQueue(int &x) {
    if(IsFull()){
        return 0;
    }
    elements[rear]=x;
    rear=(rear+1)%maxSize;
    return 1;
}
int SeqQueue::DeQueue(int &x) {
    if(IsEmpty()){
        return 0;
    }
    x=elements[front];
    front=(front+1)%maxSize;
    return 1;
}
void SeqQueue::output() {
    int i=front;
    while(i!=rear){
        cout<<elements[i]<<endl;
        i=(i+1)%maxSize;
    }
}
int main(){
    SeqQueue s;
    for(int i=0;i<3;i++){
        s.EnQueue(i);
    }
    s.output();
}

3、链式队列

#include <iostream>
using namespace std;
struct QueueNode{
    int data;
    QueueNode *link;
    QueueNode(int d=0,QueueNode *next=NULL):data(d),link(next){}
};
class LinkedQueue{
private:
    QueueNode *front,*rear;
public:
    LinkedQueue():front(NULL),rear(NULL){}
    ~LinkedQueue(){MakeEmpty();}
    void MakeEmpty();
    int EnQueue(int &x);
    int DeQueue(int &x);
    int GetFront(int &x);
    int IsEmpty()const{
        return (front==NULL)?1:0;
    }
    int getSize()const;
    void output();
};
void LinkedQueue::MakeEmpty() {
    QueueNode *p;
    while(front!=NULL){
        p=front;front=front->link;delete p;
    }
}
int LinkedQueue::EnQueue(int &x) {
    if(front==NULL){
        front=rear=new QueueNode(x);
    }
    else{
        rear->link=new QueueNode(x);
        rear=rear->link;
    }
}
int LinkedQueue::DeQueue(int &x) {
    if(IsEmpty()){
        return 0;
    }
    QueueNode *p=front;
    x=front->data;
    front=front->link;
    delete p;
    return 1;
}
int LinkedQueue::GetFront(int &x) {
    if(IsEmpty()){
        return 0;
    }
    x=front->data;
    return 1;
}
int LinkedQueue::getSize() const {
    QueueNode *p=front;
    int k=0;
    while(p!=NULL){
        k++;
        p=p->link;
    }
    return k;
}
void LinkedQueue::output() {
    QueueNode *p=front;
    int i=0;
    while(p!=NULL){
        cout<<++i<<":"<<p->data<<endl;
        p=p->link;
    }
}
int main(){
    LinkedQueue l;
    for(int i=0;i<3;i++){
        l.EnQueue(i);
    }
    l.output();
}