循环单链表的基本操作（增删改查）——C语言

一、定义

• 循环单链表与链表的性质相似，只是终端结点的指针不是指向空，而是指向头结点，判断空的条件是头结点指向下一个仍然还是头结点。

二、代码
1、定义结构体

typedef struct CirList {
        datatype data;
        struct CirList* next;
}CirList;

2、创建头结点

struct CirList* CreateList() {
        struct CirList* headNode = (struct CirList*)malloc(sizeof(struct CirList));
        headNode->next = headNode;
        return headNode;
}

3、新增结点

struct CirList* CreateNode(datatype data) {
        struct CirList* newNode = (struct CirList*)malloc(sizeof(struct CirList));
        newNode->data = data;
        newNode->next = NULL;
        return newNode;
}

4、插入操作

void insertList(struct CirList *headNode, datatype data) {
        struct CirList* newNode = CreateNode(data);
        newNode->next = headNode->next;
        headNode->next = newNode;
}		//头插法

5、删除操作

void deleteList(struct CirList* headNode, datatype posdata) {
        struct CirList* posNode = headNode->next;
        struct CirList* posNodefront = headNode;
        if (posNode == headNode) {
               printf("error:NULL!");
               return;
        }
        else {
               while (posNode->data != posdata) {
                       posNodefront = posNode;
                       posNode = posNode->next;
                       if (posNode == headNode) {
                              printf("error:null!");
                              return;
                       }
               }
               posNodefront->next = posNode->next;
               free(posNode);
        }
}

6、修改操作

void amendList(struct Node* headNode, datatype posdata,datatype data) {
        struct Node* posNode = headNode->next;
        if (posNode == headNode)
               printf("error!");
        else {
               while (posNode->data != posdata) {
                       posNode = posNode->next;
                       if (posNode == headNode) {
                              printf("error!");
                              return;
                       }
               }
               posNode->data = data;
        }
}

7、打印链表

void printList(struct CirList *headNode) {
        struct CirList* pMove = headNode->next;
        if (pMove == headNode) {
               printf("error:NULL!");
               return;
        }
        else {
               while (pMove != headNode) {
                       printf("%d\t", pMove->data);
                       pMove = pMove->next;
               }
        }
        putchar('\n');
}