双向循环链表 函数的实现

#include"list.h"void InitList(List *list){Node *s=(Node *)malloc(sizeof(Node));assert(s!=NULL);    list->first=list->last=s;list->first->prev=list->last;list->last->next=list->first;list->size=0;}void push_back(List *list, ElemType x){    Node *s=(Node *)malloc(sizeof(Node));assert(s!=NULL);s->data=x;list->last->next=s;s->prev=list->last;list->last=s;    list->first->prev=list->last;list->last->next=list->first;list->size++;}void push_front(List *list, ElemType x){    Node *s = (Node *)malloc(sizeof(Node));assert(s != NULL);s->data = x;s->prev=list->first;s->next=list->first->next;list->first=s;s->next->prev=s;        if(list->size==0)list->last=s;list->size++;}void pop_back(List *list){if(list->size==0)cout<<"表空，不能删除!"<<endl;list->last=list->last->prev;free(list->first->prev);if(list->size==1)list->last=list->first;list->first->prev=list->last;list->last->next=list->first;list->size--;}void pop_front(List *list){    if(list->size==0)cout<<"表空，不能删除!"<<endl;Node *p=list->first->next;list->first->next=p->next;p->next->prev=list->first;free(p);if(list->size==1){list->last=list->first;list->last->next=list->first;list->first->prev=list->last;}list->size--;}void show_list(List *list){Node *p = list->first->next;while(p != list->first){cout<<p->data<<"-->";p = p->next;}cout<<"Over!"<<endl;}Node* find(List *list, ElemType key){Node *p=list->first->next;while(p!=list->first&&p->data!=key)p=p->next;if(p!=list->first)return p;return NULL;}bool delete_val(List *list, ElemType key){Node *q=find(list,key);if(q==NULL)return false;if(q==list->last){list->last=q->prev;}q->prev->next=q->next;q->next->prev=q->prev;free(q);list->size--;return true;}bool insert_val(List *list, ElemType x){Node *p = find(list,x);if(p != NULL)return false;Node *s = (Node *)malloc(sizeof(Node));assert(s != NULL);s->data = x;p = list->first;while(p->next != list->first){if(x<p->next->data)break;//如果x小于第一个，则跳出循环执行下面操作p = p->next;}s->next = p->next;p->next->prev = s;s->prev = p;p->next = s;if(p == list->last)//如果x大于最后一个，将list->last指向s即可{list->last = s;}list->size++;return true;}bool resver(List *list)//从第二个节点开始按照顺序头插{Node *p = list->first->next;Node *q = p->next;p->next = list->first;list->first->prev = p;list->last = p;while(p!=list->first){p = q;q = q->next;p->next = list->first->next;p->next->prev = p;p->prev = list->first;list->first->next = p;}return true;}