数据结构 | 双向链表简单实现及图示

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双向链表

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和单向链表相比有以下优势：

插入删除不需要移动元素外，可以原地插入删除

可以双向遍历

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初始化+尾插法图示：//head始终指向头结点，p指向尾节点，方便后续算法使用

删除单个图示：

实现代码：

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <string.h>
  4 typedef struct Node pNode;
  5 struct Node
  6 {
  7     int data;
  8     pNode *prev, *next;
  9 };
 10 /* 初始化链表，尾插法 */
 11 pNode *InitList(pNode **head, int n)
 12 {
 13     pNode *p, *s;
 14     (*head) = (pNode *)malloc(sizeof(pNode));
 15     if ((*head) == NULL)
 16         exit(0);
 17     (*head)->next = NULL;//head的prev和next均指向NULL
 18     (*head)->prev = NULL;
 19     p = (*head);//p指向head
 20     int i;
 21     for (i = 0; i < n; ++i)
 22     {
 23         s = (pNode *)malloc(sizeof(pNode));
 24         if (s == NULL)
 25             exit(0);
 26         printf("Input the value of the %dth node:", i + 1);
 27         scanf("%d", &s->data);
 28         s->next = NULL;
 29         p->next = s;
 30         s->prev = p;
 31         p = s;//p指向尾节点
 32     }
 33     return p;
 34 }
 35 /* 遍历打印 */
 36 void PrintList(pNode *head)
 37 {
 38     pNode *p;
 39     p = head->next;
 40     if (head->next == NULL)
 41         printf("the list is empty\n");
 42     while(p != NULL)
 43     {
 44         printf("%d ", p->data);
 45         p = p->next;
 46     }
 47     printf("\n");
 48 }
 49 /* 清空链表 */
 50 void DeleteList(pNode **head)
 51 {
 52     pNode *p;
 53     while((*head)->next != NULL)
 54     {
 55         p = (*head);
 56         p->next->prev = NULL;
 57         (*head) = p->next;
 58         free(p);
 59     }
 60 }
 61 /* 查找链表内的某个值 */
 62 int SearchList(pNode *head)
 63 {
 64     int number;
 65     printf("Values are about to be deleted:");
 66     scanf("%d", &number);
 67     pNode *p;
 68     p = head->next;
 69     while(p != NULL)
 70     {
 71         if (p->data == number)
 72         {
 73             return number;
 74         }
 75         p = p->next;
 76     }
 77     return 0;
 78 }
 79 /* 删除链表中某个元素，令p的前驱节点和后驱节点相互指向即可，如果p是尾节点则直接将前驱节点指向NULL*/
 80 void DelNumqList(pNode **head, int n)
 81 {
 82     int i;
 83     pNode *p;
 84     p = (*head)->next;
 85     for (i = 1; i < n; ++i)
 86         p = p->next;
 87     if(p->next == NULL)
 88     {
 89         p->prev->next = NULL;
 90         free(p);
 91     }
 92     else
 93     {
 94         p->next->prev = p->prev;
 95         p->prev->next = p->next;
 96         free(p);
 97     }
 98 }
 99 int main(int argc, char const *argv[])
100 {
101     int n, element, flag;
102     pNode *head, *last;
103     /***************************************************************/
104     printf("Please input the size of the list:");
105     scanf("%d", &n);
106     last = InitList(&head, n);//初始化链表并赋值,返回尾节点last
107     printf("%d %d \n", head->next->data, last->data); //打印为第一个元素和最后一个元素
108     PrintList(head);
109     /***************************************************************/
110     flag = SearchList(head); //搜索某个值并删除节点
111     if (flag > 0 && flag <= n)
112     {
113         DelNumqList(&head, flag);
114         PrintList(head);
115     }
116     else
117         printf("Element does not exist, cannot be deleted\n");
118     /***************************************************************/
119     DeleteList(&head);//清空列表
120     PrintList(head);
121     return 0;
122 }