链表c语言实现

表是一种常用的数据结构，可以采用数组实现和链表实现。若采用数组实现，需要对表的大小进行事先估计，通常需要估计的大一些，从而会浪费一些空间，这是严重的局限，特别是在存在许多未知大小的表的情况下。

数组实现使得PrintList和FInd操作以线性时间执行，而FindKth（查找第K个元素）则花费常数时间。然而，插入和删除的花费则是昂贵的。例如，在位置0插入元素，首先需要将整个数组后移一个位置一空出空间来，而删除第一个元素则需要将表中的所有元素向前移动一个位置，因此这两种情形的最坏运行时间都为O(N)。因为数组实现插入和删除的运行时间如此的慢，并且还需要事先估计表的大小，所以表的实现一般都采用链表，包括单向链表，双向链表，循环链表等。

为了避免插入和删除的线性开销，需要允许表可以不连续存储，否则表的部分或全部需要整体移动。图1-1给出了链表的一般想法。

头文件：list.h

#ifndef _List_H#define _List_Htypedef int ElementType;struct Node;typedef struct Node *PtrToNode;typedef PtrToNode List;typedef PtrToNode Position;List MakeEmpty( List L );                             //如果L不为空，则将L的空间回收，然后重新分配空间，初始化。int IsEmpty( List L ); int IsLast( Position P, List L );                    //判断P是否是最后一个元素int Length( List L );                                //返回链表的长度Position Find( ElementType X, List L );void Delete( ElementType X, List L );                //删除X元素的节点Position FindPrevious( ElementType X, List L );      //寻找X元素的前驱，如果X不存在，返回最后一个元素void Insert( ElementType X, List L, Position P );    //在位置P之后插入元素Xvoid DeleteList( List L );                           //删除整个链表Position Header( List L );Position Advance( Position P );                      //功能就是 P = P->Next;ElementType Retrieve( Position P );                  //功能就是 X = P->Element;void PrintList( List L );List Intersect( const List A, const List B);          //两个链表的交集List Union( const List A, const List B);             //两个链表的并集List Reverse( List L );                              //转置链表，新开辟N个元素空间             List Reverse_constVolume( List L );                   //转置链表，但只耗费常量个元素空间#endif

链表实现文件：list:

#include "list.h"#include <stdlib.h>#include <iostream>using namespace std;struct Node{ElementType Element;Position Next;};List MakeEmpty(List L){if (L != NULL)DeleteList(L);L = (List)malloc(sizeof(struct Node));if (L == NULL)cout << "Out of memory!" << endl;L->Next = NULL;return L;}int IsEmpty(List L){return L->Next == NULL;}int IsLast( Position p, List L ){return p->Next == NULL;}int Length( List L ){Position P = L->Next;int len = 0;while (P != NULL){++len;P = P->Next;}return len;}Position Find(ElementType X, List L){Position p;p = L->Next;while (p != NULL && p->Element != X)p = p->Next;return p;}void Delete( ElementType X, List L ){Position p, TmpCell;p = FindPrevious(X, L);//找到X的前驱，如果X不存在，那么其前驱则是表中最后一个元素if (!IsLast(p, L)){TmpCell = p->Next;p->Next = TmpCell->Next;free(TmpCell);}}Position FindPrevious( ElementType X, List L ){Position p;p = L;while (p->Next != NULL && p->Next->Element != X)p = p->Next;return p;}void Insert( ElementType X, List L, Position P ){Position TmpCell;TmpCell = (Position)malloc(sizeof(struct Node));if (TmpCell == NULL)cout << "Out of space!!!" << endl;TmpCell->Element = X;TmpCell->Next = P->Next;P->Next = TmpCell;}void InsertNode(PtrToNode node, List L, Position P){node->Next = P->Next;P->Next = node;}void DeleteList(List L){Position P, Tmp;P = L->Next;L->Next = NULL;while (P != NULL){Tmp = P->Next;free(P);P = Tmp;}}Position Header(List L){return L;}Position First( List L ){return L->Next;}Position Advance(Position P){return P->Next;}ElementType Retrieve( Position P ){return P->Element;}void PrintList( List L ){if (!IsEmpty(L)){Position Tmp = L->Next;while(Tmp != NULL){printf("%5d", Retrieve(Tmp));Tmp = Advance(Tmp);}printf("\n");}elseprintf("The List is empty!!\n");}void Swap( Position BeforeP, List L ){if (IsLast(BeforeP->Next, L)){printf("Cannot swap!\n");return;}Position P, AfterP;P = BeforeP->Next;AfterP = P->Next;BeforeP->Next = AfterP;P->Next = AfterP->Next;AfterP->Next = P;}List Intersect( const List A, const List B){List result = NULL;result = MakeEmpty(result);Position PA = A->Next;Position PB = B->Next;Position PR = Header(result);while (PA != NULL && PB != NULL){if (PA->Element < PB->Element)PA = PA->Next;else if (PA->Element > PB->Element)PB = PB->Next;else{Insert(PA->Element, result, PR);PA = PA->Next;PB = PB->Next;PR = PR->Next;}}return result;}List Union( const List A, const List B){List result = NULL;result = MakeEmpty(result);Position PA = A->Next;Position PB = B->Next;Position PR = Header(result);while (PA != NULL && PB != NULL){if (PA->Element < PB->Element){Insert(PA->Element, result, PR);PA = PA->Next;PR = PR->Next;}else if (PA->Element > PB->Element){Insert(PB->Element, result, PR);PB = PB->Next;PR = PR->Next;}else{Insert(PA->Element, result, PR);PA = PA->Next;PB = PB->Next;PR = PR->Next;}}if (PA == NULL){PA = PB;}while (PA != NULL){Insert(PA->Element, result, PR);PA = PA->Next;PR = PR->Next;}return result;}List Reverse( List L ){int N = Length(L);ElementType *array = (ElementType *)malloc(sizeof(ElementType) * N);Position P = L->Next;int i = 0;while (P != NULL){array[i] = P->Element;++i;P = P->Next;}P = L->Next;for (i = N - 1; i >= 0; --i){P->Element = array[i];P = P->Next;}free(array);return L;}List Reverse_constVolume( List L ){Position Tmp, P = L->Next;while (P->Next != NULL){Tmp = P->Next;P->Next = Tmp->Next;Tmp->Next = L->Next;L->Next = Tmp;}return L;}