双链表正排序.c

线性顺序存储结构双链表正排序逆波兰计算器二叉排序树二叉树实例

#include<stdio.h> 
#include<stdlib.h> 
#include<malloc.h> 
struct list{ 
  int data; 
  struct list *next; 
  struct list *pre; 
  }; 
typedef struct list node; 
typedef node *link; 
link front=NULL,rear,ptr,head=NULL; 

link push(int item){ 
link newnode=malloc(sizeof(node)); 
 newnode->data=item; 
 if(head==NULL)
 {
 head=newnode; 
 head->next=NULL; 
 head->pre=NULL;
 rear=head;
 }
 else
 {
 rear->next=newnode;
 newnode->pre=rear;
 newnode->next=NULL;
 rear=newnode;
 }
 return head; 
 } 

void makenull(){           
 front=NULL; 
 rear=NULL; 
 } 

empty(){ 
  if(front==NULL) 
   return 1; 
  else 
   return 0; 
  } 

int tops(){ 
   if(empty()) 
    return NULL; 
   else 
    return rear->data; 
   } 

void pop(){ 
   if(empty()) 
    printf("stack is empty!\n"); 
   else 
    rear=rear->pre; 
   } 

void display(link l){ 
    link p; 
    p=l; 
    while(p!=NULL){ 
      printf("%d->",p->data); 
      p=p->next; 
    } 
} 


void main(){ 
int n,i; 
printf("input your first data!\n"); 
scanf("%d",&n); 
front=push(n); 
   /*another data*/ 
for(i=0;i<3;i++) 
{ 
 printf("input:\n"); 
 scanf("%d",&n); 
 push(n); 
} 
 ptr=front; 
 display(ptr); 
 printf("\n Please enter any key to pop"); 
getch();
 pop(); 
 ptr=front; 
 display(ptr); 
getch();

}