栈ADT的实现

/* 栈ADT链表实现的类型声明 */
struct Node;
typedef struct Ndoe *PtrToNode;
typedef PtrToNode Stack;

struct Node{
    ElementType Element;
    Stack Next;
};

/* 测试是否为空栈 */
int
IsEmpty( Stack S )
{
    return S->Next == NULL;
}
/* 创建空栈 */
Stack
CreateStack(void)
{
    Stack S;

    S = malloc(sizeof(struct Node));
    if(S == NULL)
        FatalError("no space");
    S->Next = NULL;
    return S;
}
/* 清空栈 */
/* 直接删除链表与无数次Pop异曲同工 */
void
MakeEmpty( Stack S)
{
    Stack p,TmpCell;
    p = S->Next;
    S->Next = NULL;
    while(p != NULL )
    {
        TmpCell = p->Next;
        free(p);
        p = TmpCell;
    }
}
/* 书上的实现方法 */
void
MakeEmpty( Stack S )
{
    if(S == NULL)
        Error("Must create a stack");
    else
    {
        while(!IsEmpty(S))
            Pop(S);
    }
}
/* Pop 例程 */
void
Pop( Stack S )
{
    PtrToNode FirstCell;
    FirstCelll = S->Next;
    S->Next = FirstCell->Next;
    free(FirstCell);
}
/* Push 进栈操作 */
void
Push( Stack S, ElementType X )
{
    PtrToNode TmpCell;
    TmpCell = malloc( sizeof( struct Node ) );
    if( TmpCell == NULL )
        FatalError("out of space");
    else
    {
        TmpCell->Element = X;
        TmpCell->Next = S->Next;
        S->Next = TmpCell;
    }
}
/* 返回栈顶元素 */
ElementType
Top( Stack S )
{
    if( IsEmpty( S ) )
        Fata
}