习题3.25 链表和数组对队列例程实现

//链表做队列

/* assume a header */

struct Node;

struct Queue;

typedef struct Node * PtrToNode;

typedef struct Queue * PtrToQ;



struct Node{

    ElementType ele;

    PtrToNode Next;

};



struct Queue{

    PtrToNode rear;

    PtrToNode front;

};



PtrToQ

CreateQ( void )

{

    PtrToQ Q;

    Q = malloc( sizeof( struct Queue ) );

    Q->rear = Q->front = malloc( sizeof( struct Node ) );

    Q->rear->next = NULL;

}



void

AddQ( ElementType X, PtrToQ Q )

{

    PtrToNode TmpCell;

    Tmpcell = malloc( sizeof( struct Node ) );

    TmpCell->ele = X;

    TmpCell->Next = NULL;

    Q->rear->Next = TmpCell;

    Q->rear = TmpCell;

}



Elementtype

DeleteQ( PtrToQ Q )

{

    ElementType res;

    PtrToNode TmpCell;

    TmpCell = Q->front->Next;

    Q->front->Next = TmpCell->Next;

    res = Tmpcell->ele;

    free( TmpCell );

    return res;

}

View Code

以上使用链表做的

以下是用数组做的

//循环数组

#define MaxSize 100

struct Queue;

typedef struct Queue * PtrToQ;



struct Queue{

    ElementType *Array;

    int front;

    int rear;

};



PtrToQ

CreateQ( int Size )

{

    PtrToQ Q;

    Q = malloc( sizeof( struct Queue ) );

    Q->Array = malloc( sizeof( ElementType ) * Size );

    Q->front = Q->rear = 0;

    return Q;

}



int 

IsFull( PtrToQ Q )

{

    return ( Q->rear + 1 ) % MaxSize == Q->front;

}



void

AddQ( ElementType X, PtrToQ Q )

{

    if( !IsFull( Q ) ){

    Q->rear = ( Q->rear + 1 ) % MaxSize;

    Q->Array[ Q->rear ] = X;

    }

    else

        Error("full")

}



int 

IsEmpty( PtrToQ Q )

{

    return Q->rear == Q->front;

}



ElementType

DeleteQ( PtrToQ Q )

{

    if( !IsEmpty( Q ) )

    {

        Q->front = ( Q->front + 1 ) % MaxSize;

        return Q->front->ele;

    }

    else

        Error();

}

View Code

在循环数组这一栏，实际上front所指向的地方实际上是没有意义但要保留的，为空