队列的实现

1. 基本操作

操作	解释
MakeNull(Q)	将队列置空
Front(Q)	返回队列第一个元素
EnQueue(x,Q)	将元素插入Q的后端
DeQueue(Q)	删除第一个元素
Empty(Q)	为空返回TRUE

2. 队列的指针实现

    struct celltype {
        Elementtype element;
        celltype *next;
    };
    
    struct QUEUE {
        celltype *front;
        celltype *rear;
    };
    
    void MakeNull(QUEUE &Q)
    {
        Q.front = new celltype;
        Q.front->next = NULL;
        Q.rear = Q.front;
    }
    
    boolean Empty(QUEUE Q) 
    {
        if(Q.front == Q.rear)
            return TRUE;
        else
            return FALSE;
    }
    
    void EnQueue(Elementtype x, QUEUE &Q) 
    {
         Q.rear->next = new celltype;
         Q.rear = Q.rear->next;
         Q.rear->element = x;
         Q.rear->next = NULL; 
    }
    
    void DeQueue(QUEUE &Q)
    {
        celltype *tmp;
        if(Empty(Q))
            error("empty");
        else
        {
            tmp = Q.front->next;
            Q.front->next = tmp->next;
            delete tmp;
            if(Q.front->next == NULL)
                Q.rear = Q.front;
        }
    }
    

3. 队列的数组实现

    #define maxlength 100
    typedef struct {
        int front;
        int rear;
        Elementtype elements[maxlength];
    } QUEUE;
    
    int addone(int i )
    {
        return (i+1)%maxlength;
    }
    
    void MakeNull(QUEUE &Q)
    {
        Q.front = 0;
        Q.rear = maxlength - 1;
    }
    
    boolean Empty(QUEUE Q)
    {
        if(addone(Q.rear) == Q.front)
            return TRUE;
        else
            return FALSE;
    }
    
    Elementtype Front(QUEUE Q)
    {
        if(Empty(Q))
            return NULL;
        else
            return Q.elemenmts[Q.front];
    }
    
    void EnQueue(elementtype x, QUEUE &Q)
    {
        if(addone(addone(Q.rear)) == Q.front)
            error("queue is full");
        else {
            Q.rear = addone(Q.rear);
            Q.elements[Q.rear] = x;
        }
    }
    
    void DeQueue(QUEUE &Q)
    {
        if(Empty(Q))
            error("queue is empty");
        else
            Q.front = addone(Q.front);
    }
    

部分资料来自《数据结构与算法--张岩》