將單鏈表中終端結點的指針端由空指針改為指向頭結點，就使整個單鏈表形成一個環，這種頭尾相接的鏈表稱為單循環鏈表，簡稱循環鏈表。

CircleLinkList.h

 1 #ifndef CIRCLELINKLIST_H
 2 #define CIRCLELINKLIST_H
 3 
 4 #include<stdio.h>
 5 #include<stdlib.h>
 6 #include<string.h>
 7 
 8 
 9 //鏈表小結點
10 typedef struct CIRCLELINKNODE {
11     struct CIRCLELINKNODE* next;
 
12 }CircleLinkNode;
13 
14 //鏈表結構體
15 typedef struct CIRCLELINKLIST {
16     CIRCLELINKNODE head;
17     int size;
18 }CircleLinkList;
19 
20 //編寫針對鏈表結構體操作的API函數
21 
22 #define TRUE 1
23 #define FALSE 0
24 
25 
26 //比較回調
27 typedef int(*COMPARENODE)(CircleLinkNode*, CircleLinkNode*);
28 //打印回調
29 typedef void
 
(*PRINTNODE)(CircleLinkNode*);
30 
31 
32 //初始化函數
33 CircleLinkList* Init_CircleLinkList();
34 //插入函數
35 void Insert_CircleLinkList(CircleLinkList* clist,int pos, CircleLinkNode* data);
36 //獲得第一個元素
37 CircleLinkNode* Front_CircleLinkList(CircleLinkList* clist);
38 //根據位置刪除
39 void RemoveByPos_CircleLinkList(CircleLinkList* clist,int
 
 pos);
40 //根據值去刪除
41 void RemoveByValue_CircleLinkList(CircleLinkList* clist, CircleLinkNode* data, COMPARENODE compare);
42 //獲得鏈表的長度
43 int Size_CircleLinkList(CircleLinkList* clist);
44 //判斷是否為空
45 int IsEmpty_CircleLinkList(CircleLinkList* clist);
46 //查找
47 int Find_CircleLinkList(CircleLinkList* clist, CircleLinkNode* data, COMPARENODE compare);
48 //打印結點
49 void Print_CircleLinkList(CircleLinkList* clist,PRINTNODE print);
50 //釋放內存
51 void FreeSpace_CircleLinkList(CircleLinkList* clist);
52 
53 
54 #endif

CircleLinkList.c

  1 #include"CircleLinkList.h"
  2 
  3 
  4 
  5 //初始化函數
  6 CircleLinkList* Init_CircleLinkList() {
  7 
  8     CircleLinkList* clist = (CircleLinkList*)malloc(sizeof(CircleLinkList));
  9     clist->head.next = &(clist->head);
 10     clist->size = 0;
 11 
 12     return clist;
 13 }
 14 //插入函數
 15 void Insert_CircleLinkList(CircleLinkList* clist, int pos, CircleLinkNode* data) {
 16     if (clist == NULL) {
 17         return;
 18     }
 19     if (data == NULL) {
 20         return;
 21     }
 22     if (pos<0 || pos>clist->size) {
 23         pos = clist->size;
 24     }
 25     //根據位置查找前一個結點
 26     //輔助指針變量
 27     CircleLinkNode* pCurrent = &(clist->head);
 28     for (int i = 0; i < pos; i++) {
 29         pCurrent = pCurrent->next;
 30     }
 31     //插入新元素
 32     data->next = pCurrent->next;
 33     pCurrent->next = data;
 34 
 35     clist->size++;
 36 }
 37 //獲得第一個元素
 38 CircleLinkNode* Front_CircleLinkList(CircleLinkList* clist) {
 39     return clist->head.next;
 40 }
 41 //根據位置刪除
 42 void RemoveByPos_CircleLinkList(CircleLinkList* clist, int pos) {
 43     if (clist == NULL) {
 44         return;
 45     }
 46     if (pos<0 || pos>clist->size) {
 47         return;
 48     }
 49     //根據pos找上一個結點
 50     //輔助指針變量
 51     CircleLinkNode* pCurrent = &(clist->head);
 52     for (int i = 0; i < pos; i++) {
 53         pCurrent = pCurrent->next;
 54     }
 55 
 56     //緩存當前結點的下一個結點
 57     CircleLinkNode* pNext = pCurrent->next;
 58     pCurrent->next = pNext->next;
 59 
 60     clist->size--;
 61 
 62 }
 63 //根據值去刪除
 64 void RemoveByValue_CircleLinkList(CircleLinkList* clist, CircleLinkNode* data, COMPARENODE compare) {
 65     if (clist == NULL) {
 66         return;
 67     }
 68     if (data == NULL) {
 69         return;
 70     }
 71     //這個是循環鏈表，不能一直循環
 72     CircleLinkNode* pPrev = &(clist->head);
 73     CircleLinkNode* pCurrent = pPrev->next;
 74     int i = 0;
 75     for (; i < clist->size; i++) {
 76         if (compare(pCurrent,data) == TRUE) {
 77             pPrev->next = pCurrent->next;
 78             break;
 79         }
 80         pPrev = pCurrent;
 81         pCurrent = pPrev->next;
 82     }
 83 
 84     clist->size--;
 85 
 86 }
 87 //獲得鏈表的長度
 88 int Size_CircleLinkList(CircleLinkList* clist) {
 89     return clist->size;
 90 }
 91 //判斷是否為空
 92 int IsEmpty_CircleLinkList(CircleLinkList* clist) {
 93     if (clist->size == 0) {
 94         return TRUE;
 95     }
 96     return FALSE;
 97 }
 98 //查找
 99 int Find_CircleLinkList(CircleLinkList* clist, CircleLinkNode* data, COMPARENODE compare) {
100     if (clist == NULL) {
101         return FALSE;
102     }
103     if (data == NULL) {
104         return FALSE;
105     }
106     CircleLinkNode* pCurrent = clist->head.next;
107     int flag = -1;
108     for (int i = 0; i < clist->size; i++) {
109         if (compare(pCurrent, data) == TRUE) {
110             flag = i;
111             break;
112         }
113         pCurrent = pCurrent->next;
114     }
115 
116     return flag;
117 }
118 //打印結點
119 void Print_CircleLinkList(CircleLinkList* clist, PRINTNODE print) {
120     if (clist == NULL) {
121         return;
122     }
123     CircleLinkNode* pCurrent = clist->head.next;
124     for (int i = 0; i < clist->size; i++) {
125         if(pCurrent==&(clist->head)){
126             pCurrent = pCurrent->next;
127             printf("-----------------\n");
128         }
129         print(pCurrent);
130         pCurrent = pCurrent->next;
131     }
132 }
133 //釋放內存
134 void FreeSpace_CircleLinkList(CircleLinkList* clist) {
135     if (clist == NULL) {
136         return;
137     }
138     free(clist);
139 }

main.c

 1 #define _CRT_SECURE_NO_WARNINGS
 2 #include<stdio.h>
 3 #include<stdlib.h>
 4 #include<string.h>
 5 #include"CircleLinkList.h"
 6 
 7 typedef struct PERSON {
 8     CircleLinkNode* node;
 9     char name[64];
10     int age;
11     int score;
12 }Person;
13 
14 void MyPrint(CircleLinkNode* data) {
15     Person* p = (Person*)data;
16     printf("Name:%s  Age:%d  Score:%d\n",p->name,p->age,p->score);
17 }
18 
19 int MyCompare(CircleLinkNode* data1, CircleLinkNode* data2) {
20     Person* p1 = (Person*)data1;
21     Person* p2 = (Person*)data2;
22     if (strcmp(p1->name, p2->name) == 0 && p1->age == p2->age && p1->score == p2->score) {
23         return TRUE;
24     }
25     return FALSE;
26 }
27 
28 int main() {
29 
30     //創建循環鏈表
31     CircleLinkList* clist = Init_CircleLinkList();
32     //創建數據
33     Person p1, p2, p3, p4, p5;
34     strcpy(p1.name, "aaa");
35     strcpy(p2.name, "bbb");
36     strcpy(p3.name, "ccc");
37     strcpy(p4.name, "ddd");
38     strcpy(p5.name, "eee");
39 
40     p1.age = 15;
41     p2.age = 16;
42     p3.age = 17;
43     p4.age = 18;
44     p5.age = 19;
45 
46     p1.score = 55;
47     p2.score = 60;
48     p3.score = 70;
49     p4.score = 80;
50     p5.score = 90;
51 
52     //數據入鏈表
53     Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p1);
54     Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p2);
55     Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p3);
56     Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p4);
57     Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p5);
58 
59 
60     //打印
61     Print_CircleLinkList(clist, MyPrint);
62 
63     Person pDel;
64     strcpy(pDel.name, "ccc");
65     pDel.age = 17;
66     pDel.score = 70;
67     //根據值刪除
68     RemoveByValue_CircleLinkList(clist, (CircleLinkNode*)&pDel, MyCompare);
69     //打印
70     printf("------------------\n");
71     Print_CircleLinkList(clist, MyPrint);
72 
73 
74     //釋放內存
75     FreeSpace_CircleLinkList(clist);
76 
77 
78 
79     system("pause");
80     return 0;
81 }

運行結果：

15、循環鏈表