C语言实现单向循环链表，主要功能为空链表创建，链表初始化（头插法，尾插法），链表元素读取，按位置插入，（有序链表）按值插入，按位置删除，按值删除，清空链表，销毁链表。
单向循环链表和单向链表的区别：（1）单向链表为头指针，循环链表为尾指针，头指针指向头结点，尾指针指向终端结点；（2）为统一方便操作，单向链表设置头结点，单向循环链表设置头结点和尾结点；（3）设置尾结点后，尾指针指向尾结点，插入，删除等操作不用移动尾指针。
关键思路：创建头结点和尾结点。
1 #include <stdio.h> 2 #include <stdlib.h> 3 4 typedef struct Node{ 5 int data; 6 struct Node *next; 7 }Node; 8 9 //空循环链表创建 10 //创建头结点和尾结点 11 //链表尾指针指向尾结点，尾结点指向头结点，头结点指向尾结点 12 void iniCList(Node **CListTail){ 13 *CListTail = (Node *)malloc(sizeof(Node)); 14 Node *CListHead = (Node *)malloc(sizeof(Node)); 15 if (NULL == *CListTail || NULL == CListHead){ 16 exit(0); 17 } 18 19 (*CListTail)->next = CListHead; 20 CListHead->next = *CListTail; 21 } 22 23 //循环链表初始化(头插法) 24 void iniCListHead(Node **CListTail, int n){ 25 //创建头尾结点 26 *CListTail = (Node *)malloc(sizeof(Node)); 27 Node *CListHead = (Node *)malloc(sizeof(Node)); 28 if (NULL == *CListTail || NULL == CListHead){ 29 exit(0); 30 } 31 32 (*CListTail)->next = CListHead; 33 CListHead->next = *CListTail; 34 35 int i = 0; 36 while (i < n){ 37 38 Node *tmpNode = (Node *)malloc(sizeof(Node)); 39 if (NULL == tmpNode){ 40 exit(0); 41 } 42 tmpNode->data = i; 43 tmpNode->next = CListHead->next; 44 CListHead->next = tmpNode; 45 ++i; 46 } 47 } 48 49 //循环链表初始化(尾插法) 50 void iniCListTail(Node **CListTail, int n){ 51 //创建头尾结点 52 *CListTail = (Node *)malloc(sizeof(Node)); 53 Node *CListHead = (Node *)malloc(sizeof(Node)); 54 if (NULL == *CListTail || NULL == CListHead){ 55 exit(0); 56 } 57 58 (*CListTail)->next = CListHead; 59 CListHead->next = *CListTail; 60 61 Node *pCurrent = CListHead; 62 63 int i = 0; 64 while (i < n){ 65 Node *tmpNode = (Node *)malloc(sizeof(Node)); 66 if (NULL == tmpNode){ 67 exit(0); 68 } 69 tmpNode->data = i; 70 tmpNode->next = *CListTail; 71 pCurrent->next = tmpNode; 72 pCurrent = tmpNode; 73 74 ++i; 75 } 76 } 77 78 //循环链表按位置插入 79 void insertCListPos(Node *CList, int pos, int val){ 80 81 Node *pCurrent = CList->next; //指向头结点 82 int i = 1; 83 while (pCurrent != CList && i < pos){ 84 pCurrent = pCurrent->next; 85 ++i; 86 } 87 88 Node *tmpNode = (Node *)malloc(sizeof(Node)); 89 if (NULL == tmpNode){ 90 exit(0); 91 } 92 tmpNode->data = val; 93 tmpNode->next = pCurrent->next; 94 pCurrent->next = tmpNode; 95 96 } 97 98 //有序循环链表，按值插入 99 void insertCListValue(Node *CList, int val){ 100 Node *pCur = CList->next->next; 101 Node *pPer = CList->next; 102 103 while (pCur != CList && pCur->data < val){ 104 pPer = pCur; 105 pCur = pCur->next; 106 } 107 108 Node *tmpNode = (Node *)malloc(sizeof(Node)); 109 if (NULL == tmpNode){ 110 exit(0); 111 } 112 tmpNode->data = val; 113 tmpNode->next = pPer->next; 114 pPer->next = tmpNode; 115 } 116 117 //循环链表，按位置删除 118 void deleteCListPos(Node *CList, int pos){ 119 Node *pCur = CList->next; 120 121 int i = 1; 122 while (pCur != CList && i < pos){ 123 pCur = pCur->next; 124 ++i; 125 } 126 127 Node *tmpNode = pCur->next; 128 pCur->next = tmpNode->next; 129 free(tmpNode); 130 } 131 132 //循环链表，按值删除 133 //删除空链表为出问题 134 void deleteCListValue(Node *CList, int val){ 135 Node *pCur = CList->next->next; 136 Node *pPer = CList->next; 137 138 while (pCur != CList && pCur->data != val){ 139 pPer = pCur; 140 pCur = pCur->next; 141 } 142 if (pCur == CList) 143 return; 144 else{ 145 pPer->next = pCur->next; 146 free(pCur); 147 } 148 } 149 150 //循环链表，清空链表 151 void claerCList(Node *CList){ 152 Node *p = CList->next->next; 153 Node *q = NULL; 154 155 while (p != CList){ //到达表尾 156 q = p->next; 157 free(p); 158 p = q; 159 } 160 161 CList->next = CList; //将头结点指向尾结点 162 } 163 164 //循环链表，销毁链表 165 void destoryCList(Node **CList){ 166 Node *p = (*CList)->next; 167 Node *q = NULL; 168 169 while (p != (*CList)->next){ //到达表头 170 q = p->next; 171 free(p); 172 p = q; 173 } 174 175 *CList = NULL; 176 } 177 178 //获取元素 179 void getCList(Node *CList, int pos, int *val){ 180 Node *pCur = CList->next->next; 181 int i = 1; 182 while (pCur != CList && i < pos){ 183 pCur = pCur->next; 184 ++i; 185 } 186 187 *val = pCur->data; 188 } 189 //遍历输出元素 190 void printCList(Node *CList){ 191 Node * tmpNode = CList->next->next; 192 while (tmpNode != CList){ //到达表尾 193 printf("%d\n", tmpNode->data); 194 tmpNode = tmpNode->next; 195 } 196 } 197 198 199 int main(){ 200 Node *CList = NULL; 201 //iniCListHead(&CList, 8); 202 //iniCList(&CList); 203 iniCListTail(&CList, 8); 204 205 //insertCListPos(CList, 1, 2); 206 //insertCListPos(CList, 2, 4); 207 //insertCListPos(CList, 3, 6); 208 // 209 //insertCListValue(CList, 1); 210 // 211 //deleteCListPos(CList, 3); 212 // 213 //deleteCListValue(CList, 6); 214 215 //claerCList(CList); 216 217 int a = 0; 218 getCList(CList, 2, &a); 219 printf("%d\n", a); 220 221 printCList(CList); 222 223 printf("%d\n", CList); 224 destoryCList(&CList); 225 printf("%d\n", CList); 226 227 system("pause"); 228 return 0; 229 }