• 运行结果
• 

   

• 链表定义
  typedef struct LinkNode{    int data;    struct LinkNode *pNext;}node,*PNODE;

   

• 环形链表尾部添加
  1 //尾部添加 2 PNODE addback(PNODE phead, int data) 3 { 4     //分配空间 5     PNODE pnew = (PNODE)malloc(sizeof(node)); 6     pnew->data = data; 7     if (phead == NULL) 8     { 9         phead = pnew;10         pnew->pNext = phead;11     }12     else13     {14         //循环到尾部15         PNODE p = phead;16         while (p->pNext != phead)17         {18             p = p->pNext;19         }20         p->pNext = pnew;21         //头尾相连22         pnew->pNext = phead;23     }24 25     return phead;26 }

   

• 环形链表头部添加
  1 //头部添加 2 PNODE addfront(PNODE phead, int data) 3 { 4     //分配空间 5     PNODE pnew = (PNODE)malloc(sizeof(node)); 6     pnew->data = data; 7     if (phead == NULL) 8     { 9         phead = pnew;10         pnew->pNext = phead;11     }12     else13     {14         PNODE p = phead;15         while (p->pNext != phead)16         {17             p = p->pNext;18         }19         //新的结点插在头结点之前20         pnew->pNext = phead;21         //尾结点指向头结点22         p->pNext = pnew;23         //新的结点赋值给头结点24         phead = pnew;25     }26     return phead;27 }

   

• 显示数据
  1 void showall(PNODE phead) 2 { 3     if (phead == NULL) 4     { 5         return; 6     } 7     else if (phead->pNext == phead) 8     { 9         printf("%d,%p,%p\n", phead->data, phead, phead->pNext);10     }11     else12     {13         PNODE p = phead;14         while (p->pNext != phead)15         {16             printf("%d,%p,%p\n", p->data, p, p->pNext);17             p = p->pNext;18         }19         printf("%d,%p,%p\n", p->data, p, p->pNext);20     }21 }

   

• 查找第一个指定元素
  PNODE findfirst(PNODE phead, int data){    if (phead == NULL)    {        return NULL;    }    else if (phead->pNext == phead)    {        if (phead->data == data)        {            return phead;        }    }    else    {        PNODE p = phead;        while (p->pNext != phead)        {            if (p->data == data)            {                return p;            }            p = p->pNext;        }        if (p->data == data)        {            return p;        }    }    return NULL;}

   

• 删除指定结点  判断有几个结点1.1个 2.大于一个(大于一个要判断是否是头结点)
  1 PNODE deletefirst(PNODE phead, int data) 2 { 3     //p2用于保存p1的前一个位置 4     PNODE p1 = NULL; 5     PNODE p2 = NULL; 6     p1 = phead; 7  8     //如果只有 一个结点 9     if (p1->pNext == phead)10     {11         if (p1->data == data)12         {13             return NULL;14         }15         else16         {17             return phead;18          }19     }20     //如果结点数大于一个21     else22     {23         //先判断头结点,如果头结点是则要删除头结点24         if (phead->data == data)25         {26             //遍历到尾部27             while (p1->pNext != phead)28             {29                 p1 = p1->pNext;30             }31             //尾部的后一个结点是头结点的后一个结点32             p1->pNext = phead->pNext;33             //释放头结点34             free(phead);35             //把尾接电脑的后一个赋给phead36             phead = p1->pNext;37         }38         else39         {40             //如果头结点不是要删除的结点,则从后一个开始遍历,p2保存p1移动前的位置41             p2 = p1;42             p1 = phead->pNext;43             //遍历到头结点44             while (p1 != phead)45             {46                 if (p1->data == data)47                 {48                     break;49                 }50                 else51                 {52                     p2 = p1;53                     p1 = p1->pNext;54                 }55             }56             //判断是否找到结点57             if (p1 != phead)58             {59                 p2->pNext = p1->pNext;60                 free(p1);61             }62         }63         return phead;64     }    65 }

   

• 统计有多少个结点
  1 int getnum(PNODE phead) 2 { 3     if (phead == NULL) 4     { 5         return 0; 6     } 7     else 8     { 9         int num = 1;10         PNODE p = phead;11         while (p->pNext != phead)12         {13             num++;14             p = p->pNext;15         }16         return num;17     }18 }

   

• 在指定元素之后插入一个数据 先判断有几个结点 1.1个  2.大于1个
  1 PNODE insertfirst(PNODE phead, int finddata, int data) 2 { 3     PNODE pnew = (PNODE)malloc(sizeof(node)); 4     pnew->data = data; 5  6     if (phead == NULL) 7     { 8         return NULL; 9     }10     //如果只有一个结点11     else if (phead->pNext == phead)12     {13         if (phead->data == finddata)14         {15             phead->pNext = pnew;16             pnew->pNext = phead;17             return phead;18         }19     }20     else21     {22         PNODE p = phead;23         while (p->pNext != phead)24         {25             if (p->data == finddata)26             {27                 pnew->pNext = p->pNext;28                 p->pNext = pnew;29                 return phead;30             }31             p = p->pNext;32         }33         if (p->data == finddata)34         {35             p->pNext = pnew;36             pnew->pNext = phead;37             return phead;38         }39     }40 41 }

   

• 完整代码:
  1 #include 
         
            2 #include 
          
             3   4 typedef struct LinkNode  5 {  6     int data;  7     struct LinkNode *pNext;  8 }node,*PNODE;  9  10 //尾部添加 11 PNODE addback(PNODE phead, int data) 12 { 13     //分配空间 14     PNODE pnew = (PNODE)malloc(sizeof(node)); 15     pnew->data = data; 16     if (phead == NULL) 17     { 18         phead = pnew; 19         pnew->pNext = phead; 20     } 21     else 22     { 23         //循环到尾部 24         PNODE p = phead; 25         while (p->pNext != phead) 26         { 27             p = p->pNext; 28         } 29         p->pNext = pnew; 30         //头尾相连 31         pnew->pNext = phead; 32     } 33  34     return phead; 35 } 36  37 //头部添加 38 PNODE addfront(PNODE phead, int data) 39 { 40     //分配空间 41     PNODE pnew = (PNODE)malloc(sizeof(node)); 42     pnew->data = data; 43     if (phead == NULL) 44     { 45         phead = pnew; 46         pnew->pNext = phead; 47     } 48     else 49     { 50         PNODE p = phead; 51         while (p->pNext != phead) 52         { 53             p = p->pNext; 54         } 55         //新的结点插在头结点之前 56         pnew->pNext = phead; 57         //尾结点指向头结点 58         p->pNext = pnew; 59         //新的结点赋值给头结点 60         phead = pnew; 61     } 62     return phead; 63 } 64  65 //显示数据 66 void showall(PNODE phead) 67 { 68     if (phead == NULL) 69     { 70         return; 71     } 72     else if (phead->pNext == phead) 73     { 74         printf("%d,%p,%p\n", phead->data, phead, phead->pNext); 75     } 76     else 77     { 78         PNODE p = phead; 79         while (p->pNext != phead) 80         { 81             printf("%d,%p,%p\n", p->data, p, p->pNext); 82             p = p->pNext; 83         } 84         printf("%d,%p,%p\n", p->data, p, p->pNext); 85     } 86 } 87  88 //查找第一个指定元素 89 PNODE findfirst(PNODE phead, int data) 90 { 91     if (phead == NULL) 92     { 93         return NULL; 94     } 95     else if (phead->pNext == phead) 96     { 97         if (phead->data == data) 98         { 99             return phead;100         }101     }102     else103     {104         PNODE p = phead;105         while (p->pNext != phead)106         {107             if (p->data == data)108             {109                 return p;110             }111             p = p->pNext;112         }113         if (p->data == data)114         {115             return p;116         }117     }118 119     return NULL;120 }121 122 //删除指定结点  判断有几个结点1.1个 2.大于一个(大于一个要判断是否是头结点)123 PNODE deletefirst(PNODE phead, int data)124 {125     //p2用于保存p1的前一个位置126     PNODE p1 = NULL;127     PNODE p2 = NULL;128     p1 = phead;129 130     //如果只有 一个结点131     if (p1->pNext == phead)132     {133         if (p1->data == data)134         {135             return NULL;136         }137         else138         {139             return phead;140          }141     }142     //如果结点数大于一个143     else144     {145         //先判断头结点,如果头结点是则要删除头结点146         if (phead->data == data)147         {148             //遍历到尾部149             while (p1->pNext != phead)150             {151                 p1 = p1->pNext;152             }153             //尾部的后一个结点是头结点的后一个结点154             p1->pNext = phead->pNext;155             //释放头结点156             free(phead);157             //把尾接电脑的后一个赋给phead158             phead = p1->pNext;159         }160         else161         {162             //如果头结点不是要删除的结点,则从后一个开始遍历,p2保存p1移动前的位置163             p2 = p1;164             p1 = phead->pNext;165             //遍历到头结点166             while (p1 != phead)167             {168                 if (p1->data == data)169                 {170                     break;171                 }172                 else173                 {174                     p2 = p1;175                     p1 = p1->pNext;176                 }177             }178             //判断是否找到结点179             if (p1 != phead)180             {181                 p2->pNext = p1->pNext;182                 free(p1);183             }184         }185         return phead;186     }    187 }188 189 //统计有多少个结点190 int getnum(PNODE phead)191 {192     if (phead == NULL)193     {194         return 0;195     }196     else197     {198         int num = 1;199         PNODE p = phead;200         while (p->pNext != phead)201         {202             num++;203             p = p->pNext;204         }205         return num;206     }207 }208 209 //在指定元素之后插入一个数据 先判断有几个结点 1.1个  2.大于1个210 PNODE insertfirst(PNODE phead, int finddata, int data)211 {212     PNODE pnew = (PNODE)malloc(sizeof(node));213     pnew->data = data;214 215     if (phead == NULL)216     {217         return NULL;218     }219     //如果只有一个结点220     else if (phead->pNext == phead)221     {222         if (phead->data == finddata)223         {224             phead->pNext = pnew;225             pnew->pNext = phead;226             return phead;227         }228     }229     else230     {231         PNODE p = phead;232         while (p->pNext != phead)233         {234             if (p->data == finddata)235             {236                 pnew->pNext = p->pNext;237                 p->pNext = pnew;238                 return phead;239             }240             p = p->pNext;241         }242         if (p->data == finddata)243         {244             p->pNext = pnew;245             pnew->pNext = phead;246             return phead;247         }248     }249 250 }251 252 void main()253 {254     PNODE phead = NULL;//头结点255 256     //添加257     for (int i = 1; i <= 10; i++)258     {259         phead = addback(phead, i);//插入数据260     }261     showall(phead);262     printf("\n\n");263 264     ////查找265     //PNODE pfind = findfirst(phead, 6);266     //pfind->data = 30;267 268     //删除269     /*phead = deletefirst(phead, 1);270     showall(phead);271     printf("\n\n");*/272 273     //printf("结点个数:%d\n", getnum(phead));274 275     //指定元素之后插入数据276     /*phead = insertfirst(phead, 0,100);277     showall(phead);278     printf("\n\n");*/279     //p是首地址280     PNODE p = phead;281     while (getnum(phead) != 1)282     {283         //往后数四下,然后删除284         for (int i = 0; i < 4; i++)285         {286             p = p->pNext;287         }288         PNODE pback = p->pNext;//备份p的后一个结点的位置,否则删除后p就被回收,不能再使用了289         phead = deletefirst(phead, p->data);290         p = pback;291 292         showall(phead);293         printf("\n\n");294     }295     system("pause");296 }