数据结构单向链表

单向链表主要操作有：

判断链表为空、查找、删除元素、插入元素、找前一个元素、删除链表...

需要分清楚链表的单元结构
List, Position 都是 Node, 但 List 只是入口 Node, 如果 List 中的指针为空链表就为空, 其他节点都是 Posit

 1 /* List.h */
 2 #ifndef _List_H
 3 #define _List_H
 4 
 5 struct Node;
 6 typedef struct Node *PtrToNode;
 7 typedef PtrToNode List;
 8 typedef PtrToNode Position;
 9 typedef int ElementType;
10 
11 List MakeEmpty(List L);
12 int IsEmpty(List L);
13 int IsLast(Position P, List L);
14 Position Find(ElementType X, List L);
15 void Delete(ElementType X, List L);
16 Position FindPrevious(ElementType X, List L);
17 void Insert(ElementType X, List L, Position P);
18 void DeletList(List L);
19 
20 struct Node
21 {
22     ElementType Element;
23     Position Next;
24 };
25 
26 #endif

 1 /* List.cpp */
 2 #include "List.h"
 3 #include <stdlib.h>
 4 #include <stdio.h>
 5 
 6 // Return true if L is empty, 测试链表是否为空表
 7 int IsEmpty(List L)
 8 {
 9     return L->Next == NULL;
10 }
11 
12 // Return true if P is the last position in list L
13 // Parameter L is unused in this implementation
14 // 测试当前位置是否是链表末尾
15 int IsLast(Position P, List L)
16 {
17     return P->Next == NULL;
18 }
19 
20 // Return Position of X in L; NULL if not found
21 Position Find(ElementType X, List L)
22 {
23     Position P;
24     P = L->Next;
25     while(P != NULL && P->Element != X)
26         P = P->Next;
27 
28     return P;
29 }
30 
31 void Delete(ElementType X, List L)
32 {
33     Position P, TmpCell;
34 
35     P = FindPrevious(X, L);
36 
37     if (!IsLast(P, L))
38     {
39         TmpCell = P->Next;
40         P->Next = TmpCell->Next;  //P->Next->Next;
41         free(TmpCell);
42     }
43 }
44 Position FindPrevious(ElementType X, List L)
45 {
46     Position P;
47 
48     P = L;
49     while(P->Next != NULL && P->Next->Element != X)
50         P = P->Next;
51 
52     return P;
53 }
54 
55 // Insert (after legal position)
56 // Header implementation assumed
57 // Parameter L is unused in this implementation
58 void Insert(ElementType X, List L, Position P)
59 {
60     Position TmpCell;
61 
62     TmpCell = (struct Node*)malloc(sizeof(struct Node));
63     if (TmpCell == NULL)
64         printf("Fatal Error: Out of space!!");
65 
66     TmpCell->Element = X;
67     TmpCell->Next = P->Next;
68     P->Next = TmpCell;
69 }
70 
71 void DeleteList(List L)
72 {
73     Position P, Tmp;
74 
75     P = L->Next;
76     L->Next = NULL; // Header assumed
77     while(P != NULL)
78     {
79         Tmp = P->Next;
80         free(P);
81         P = Tmp;
82     }
83 }

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