链表的游标实现

数据结构与算法分析——c语言描述 第三章 链表的游标实现

和普通的链表没什么区别，就是用数组来实现内存空间，并且存在两个链表，一个是未使用元素组成的链表，首元素是下标为0。另一个个就是使用中的数表。使用之前要main函数手动初始化。

cursor.h

typedef int ElementType;
#define SpaceSize 100
#ifndef _Cursor_H
#define _Cursor_H

typedef int PtrToNode;
typedef PtrToNode List;
typedef PtrToNode Position;

void InitializeCursorSpace(void);

List creatList();
List MakeEmpty(List L);
int IsEmpty(List L);
int IsLast(Position P, List L);
Position Find(ElementType X, List L);
void Delete(ElementType X, List L);
Position FindPrevious(ElementType X, List L);
void Insert(ElementType X, List L, Position P);
void DeleteList(List L);
Position Header(List L);
Position First(List L);
Position Advance(Position P);
ElementType Retrieve(Position P);
#endif

cursor.c

#include"cursor.h"
#include<stdlib.h>
#include"fatal.h"

struct  Node
{
ElementType Element;
Position Next;
};

struct Node CursorSpace[SpaceSize];

static List CursorAlloc() {
Position p;
p = CursorSpace[0].Next;
CursorSpace[0].Next = CursorSpace[p].Next;
return p;
}

static void Recover(Position p) {
CursorSpace[p].Next = CursorSpace[0].Next;
CursorSpace[0].Next = p;
}

void InitializeCursorSpace(void) {
for (int i = 0; i < SpaceSize - 1; i++)
CursorSpace[i].Next = i+1;
CursorSpace[SpaceSize - 1].Next = 0;
}

List creatList() {
List L;
L = CursorAlloc();
if (L == 0)
FatalError("Out of memory");
CursorSpace[L].Next = 0;
return L;
}

List MakeEmpty(List L) {
if (L != 0){
DeleteList(L);
CursorSpace[L].Next = 0;
return L;
}
else {
L = CursorAlloc();
if (L == 0)
FatalError("Out of memory");
CursorSpace[L].Next = 0;
return L;
}
}

int IsEmpty(List L) {
return CursorSpace[L].Next == 0;
}

int IsLast(Position P, List L) {
return CursorSpace[P].Next == 0;
}

Position Find(ElementType X, List L) {
Position P;
P = CursorSpace[L].Next;
while (P != 0 &&CursorSpace[P].Element != X)
{
P = CursorSpace[P].Next;
}
return P;
}

void Delete(ElementType X, List L) {
Position P;
P = FindPrevious(X, L);
if (!IsLast(P, L)) {
Position TmpCell = CursorSpace[P].Next;
CursorSpace[P].Next = CursorSpace[TmpCell].Next;
Recover(TmpCell);
}
}

Position FindPrevious(ElementType X, List L) {
Position P;
P = L;
while (CursorSpace[P].Next != 0 && CursorSpace[CursorSpace[P].Next].Element != X)
P = CursorSpace[P].Next;
return P;
}

void Insert(ElementType X, List L, Position P) {
Position tmpCell;
tmpCell = CursorAlloc();
if (tmpCell == 0)
FatalError("Out of space!!");
CursorSpace[tmpCell].Element = X;
CursorSpace[tmpCell].Next = CursorSpace[P].Next;
CursorSpace[P].Next = tmpCell;
}

void DeleteList(List L) {
Position p;
p = CursorSpace[L].Next;
CursorSpace[L].Next = 0;
while (p != 0) {
Position tmp;
tmp = CursorSpace[p].Next;
Recover(p);
p = tmp;
}
}

Position Header(List L) {
return L;
}

Position First(List L) {
return CursorSpace[L].Next;
}

Position Advance(Position P) {
return CursorSpace[P].Next;
}

ElementType Retrieve(Position P) {
return CursorSpace[P].Element;
}

main.c

#include<stdio.h>
#include"cursor.h"

int main() {
InitializeCursorSpace();
List l = creatList();
Insert(23333, l, l);
printf("%d", Retrieve(First(l)));
}