《面試準備》C++數組、鏈表實現隊列

1、數組實現隊列（加了模板）

#include <iostream>
using namespace std;
#define MAX 100
//數組實現隊列:模板類
template<class T>
class MyList
{
public:
    T * buf;
    T front;
    T rear;
public:
    MyList();
    ~MyList(){
        delete [] buf;
        buf = NULL;
        cout<<"delete MyList"<<endl;
    }
    bool isempty();
    bool isfull();
    void push_back(T a);
    T pop();   //返回棧頂元素
    void ergodic();
};

template<class T>
MyList<T>::MyList(){
    buf = new T[MAX];
    front = 0;
    rear = 0;
}

template<class T>
bool MyList<T>::isempty(){
    if(front==rear)
        return true;
    return false;
}

template<class T>
bool MyList<T>::isfull(){
    if((rear+1)%MAX==front)
        return true;
    return false;
}

template<class T>
void MyList<T>::push_back(T a){
    if(isfull()){
        return;
    }
    buf[rear] = a;
    rear = (rear+1)%MAX;
}

template<class T>
T MyList<T>::pop(){
    if(isempty()){
        return -1;
    }
    T pop_num = buf[front];
    front = (front+1)%MAX;
    return pop_num;
}

template<class T>
void MyList<T>::ergodic(){
    if(isempty()){
        return;
    }
    if(rear>front){
        for(int i=front;i<=rear-1;i++){
            cout<<"ergodic : "<<buf[i]<<endl;
        }
    }else if(rear<front){
        for(int i=front;i<MAX;i++){
            cout<<"ergodic : "<<buf[i]<<endl;
        }
        for(int i=0;i<rear;i++){
            cout<<buf[i]<<endl;
        }
    }
}

int main ()
{
    MyList<int> *mylist =new MyList<int>();
    mylist->push_back(5);
    mylist->push_back(4);
    mylist->push_back(3);
    mylist->ergodic();
    cout<<"front is : "<<mylist->pop()<<endl;
    cout<<"front is : "<<mylist->pop()<<endl;
    delete mylist; //調用析構函數，釋放內存
    mylist = NULL; //講指針指向NULL 否則將成爲野指針
    return 0;
}

2、鏈表實現隊列

#include <iostream>
#include <stack>
using namespace std;

//單向鏈表節點
struct ListNode{
    int value;
    struct ListNode *Next;
};

class MyQueue
{
public:                           //成員變量位置
    ListNode *Head;
public:                           //成員函數位置
    MyQueue(){
        Head = new ListNode;      //創建對象的時候調用
    }
    ~MyQueue(){                   //析構函數一般用於釋放內存
        delete Head;
        Head = NULL;
    }
    bool isempty();
    void pushback(int n);
    void pop();
    void ergodic();
};

bool MyQueue::isempty(){
    ListNode *P = Head;
    if(P==NULL||P->Next==NULL)
        return true;
    return false;
}

void MyQueue::pushback(int n){
    ListNode *P = Head;
    while(P->Next!=NULL){
        P = P->Next;
    }
    ListNode *tmp = new ListNode;
    tmp->value = n;
    tmp->Next =NULL;
    P->Next = tmp;
    P = tmp;
}

//只有pop不一樣，隊列是刪除第一個節點，棧是刪除最後一個節點
void MyQueue::pop(){
    if(isempty())
        return;
    ListNode *P = Head;
    P->Next = P->Next->Next;
}

void MyQueue::ergodic(){
    if(isempty())
        return;
    ListNode *P = Head;
    while(P->Next!=NULL){
        P = P->Next;
        cout<<P->value<<endl;
    }
}

int main ()
{
    MyQueue *mystack = new MyQueue;    //自己定義一個對象
    mystack->pushback(2);
    mystack->pushback(3);
    mystack->pushback(4);
    mystack->pop();
    mystack->ergodic();
    delete mystack;
    mystack = NULL;
    return 0;
}