摘要：本文介绍双向链表的实现：创建、插入、删除，以及宏定义版本

所谓双链表即每个节点有两个指针：prev指向前一个节点，next指向后一个节点

struct node {int data;struct node *prev;struct node *next;
};

首先需要创建节点：

struct node* create_node(int data) {struct node* newnode = (struct node*)malloc(sizeof(struct node));if(newnode == NULL) {printf("内存分配失败")；exit(1);}newnode->prev = NULL;newnode->next = NULL;newnode->data = data;return newnode;
}

对节点进行插入操作：

1.头插法

void insert(struct node **head, int data) {struct node *newnode = create_node(data);if (*head == NULL){*head = newnode;return;}newnode->next = *head;(*head)->prev = newnode;*head = newnode;
}

2.尾插法：

void insert(struct node **head, int data) {struct node *newnode = create_node(data);struct node *current = *head;if (current->next != NULL) {current = current->next;}current->next = newnode;newnode->prev = current;
}

删除一个节点：分为表头、表中、表尾

void delete(struct node**head, int data) {int status = 0;struct node *current = *head;while (current != NULL) {//从头节点遍历到最后一个节点if (current->data == data) {status = 1;//找到了break;}current = current->next;}if (!status) printf("未找到该数据所在节点\n");else {//节点在表尾if(current->next == NULL) {if (current->prev != NULL) // 先判断current->prev->next = NULL;free(current);}else if(current->prev == NULL) {//*******节点在表头!需要修改*head！***********head = current->next;if(current->next != NULL)current->next->prev = NULL;//考虑删除该节点为唯一的节点的情况free(current);}else{//节点在表中current->prev->next = current->next;current->next->prev = current->prev;free(current);}(current) = NULL; /* 将current置为NULL 避免悬空指针（悬空指针指向一个已经被释放的空间的地址，没有访问权限）*/}
}

宏定义头插法： list是链表头指针，item是要插入的指针

#define LIST_INSERT(item, list) do {\if ((item) != NULL) {\(item)->prev = NULL;\if ((list) != NULL) {\(item)->next = (list);\(list)->prev = (item);\} else {\(item)->next = NULL;\}\(list) = (item);\ // 更新头指针}\
} while(0)

宏定义尾插法：

#define LIST_APPEND(item, list) do {\if ((item) != NULL) {\if ((list) == NULL) {\(list) = (item);\(item)->prev = NULL;\} else {\ListNode *temp = (list);\while (temp->next != NULL) {\temp = temp->next;\}\temp->next = (item);\(item)->prev = temp;\}\(item)->next = NULL;\ }\
} while(0)

宏定义删除节点： 提供要删除的指针，进行删除

#define LIST_REMOVE(item, list) do {\if ((item) != NULL) {\if ((item)->prev != NULL) (item)->prev->next = (item)->next;\if ((item)->next != NULL) (item)->next->prev = (item)->prev;\if ((list) == (item)) (list) = (item)->next;\(item)->prev = (item)->next = NULL;\}\
} while(0)

宏定义查找删除节点：根据节点的data数据，先查找后删除：

#define DELETE_NODE(head, data) do {\int status = 0;\struct node *current = *(head);\while (current != NULL) {\if (current->data == data) {\status = 1;\break;\}\current = current->next;\}\if (!status) {\printf("未找到该数据所在节点\n");\} else {\struct node *temp = current;\if (current->next == NULL) {\if (current->prev != NULL)\current->prev->next = NULL;\free(temp);\} else if (current->prev == NULL) {\*(head) = current->next;\current->next->prev = NULL;\free(temp);\} else {\current->prev->next = current->next;\current->next->prev = current->prev;\free(temp);\}\(current) = NULL; /* 将current置为NULL 避免悬空指针*/\}\
} while(0)

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