伸展树声明和初始化

//北京邮电大学 计算机学院 Spider

#ifndef _Splay_H

struct SplayNode;
typedef struct SplayNode *SplayTree;

SplayTree MakeEmpty(SplayTree T);
SplayTree Find(ElementType X, SplayTree T);
SplayTree FindMin(SplayTree T);
SplayTree FindMax(SplayTree T);
SplayTree Initialize(void);
SplayTree Insert(ElementType X, SplayTree T);
SplayTree Remove(ElementType X, SplayTree T);
ElementType Retrieve(SplayTree T);

#endif

struct SplayNode
{
    ElementType Element;
    SplayTree Left;
    SplayTree Right;
};

typedef struct SplayNode *Position;
static Position NullNode = NULL;

SplayTree Initialize(void)
{
    if(NullNode == NULL)
    {
        NullNode = malloc(sizeof(struct SplayNode);
        if(NullNode == NULL)
            FatalError("Out of space!!!");
        NullNode->Left = NullNode->Right = NullNode;
    }
    return NullNode;
}