PTA--双向链表模拟Deque

#include <stdio.h>
#include <stdlib.h>
#include <cstring>
#define ElementType int
#define ERROR 1e5
typedef enum { push, pop, inject, eject, end } Operation;
typedef struct Node *PtrToNode;
struct Node
{
ElementType Element;
PtrToNode Next, Last;
};
typedef struct DequeRecord *Deque;
struct DequeRecord
{
PtrToNode Front, Rear;
};
Deque CreateDeque()
{
Deque q=(Deque)malloc(sizeof(struct DequeRecord));
q->Front=(PtrToNode)malloc(sizeof(struct Node));
q->Front->Last=NULL;
q->Rear=q->Front;//初始状态头和尾指向同一个位置
q->Rear->Next=NULL;
return q;
}
//Insert item X on the front end of deque D.
int Push( ElementType X, Deque D )
{
struct Node* tmp=(struct Node *)malloc(sizeof(struct Node));
tmp->Element=X;
if(D->Front==D->Rear)
{//第一个元素，特殊处理,front->元素(更新为rear)
D->Front->Next=tmp;
tmp->Last=D->Front;
D->Rear=tmp;
tmp->Next=NULL;
return 1;
}
//front->元素->...->元素(新的rear)
tmp->Next=D->Front->Next;
D->Front->Next->Last=tmp;
D->Front->Next=tmp;
tmp->Last=D->Front;
return 1;
}
//Remove the front item from deque D and return it.
ElementType Pop( Deque D )
{
if(D->Front==D->Rear) return ERROR;
int tmp=D->Front->Next->Element;
struct Node* pre=D->Front->Next;
if(D->Front->Next==D->Rear)
{//一个元素的特殊情况
D->Rear=D->Front;
D->Rear->Next=NULL;
free(pre);
return tmp;
}
D->Front->Next->Next->Last=D->Front;
D->Front->Next=D->Front->Next->Next;
free(pre);
return tmp;
}
// Insert item X on the rear end of deque D.
int Inject( ElementType X, Deque D )
{
struct Node* tmp=(struct Node *)malloc(sizeof(struct Node));
tmp->Element=X;
if(D->Rear==D->Front)
{//第一个元素，特殊处理,front->元素(更新为rear)
D->Front->Next=tmp;
tmp->Last=D->Front;
D->Rear=tmp;
tmp->Next=NULL;
return 1;
}
tmp->Last=D->Rear;
D->Rear->Next=tmp;
tmp->Next=NULL;
D->Rear=tmp;
return 1;
}
//Remove the rear item from deque D and return it. Write routines to support the deque that take O(1) time per operation.
ElementType Eject( Deque D )
{
if(D->Front==D->Rear) return ERROR;
int tmp=D->Rear->Element;
struct Node* pre=D->Rear;
D->Rear=D->Rear->Last;
D->Rear->Next=NULL;
free(pre);
return tmp;
}
Operation GetOp()
{
char op[11];
scanf("%s",op);
if(strcmp(op,"Push")==0) return push;
if(strcmp(op,"Pop")==0) return pop;
if(strcmp(op,"Inject")==0) return inject;
if(strcmp(op,"Eject")==0) return eject;
return end;
}/* details omitted */
void PrintDeque( Deque D )
{
struct Node* tmp=D->Front->Next;
printf("Inside Deque: ");
if(tmp) printf("%d",tmp->Element),tmp=tmp->Next;
else return;
while(tmp)
{
printf(" %d",tmp->Element);
tmp=tmp->Next;
}
}/* details omitted */
int main()
{
ElementType X;
Deque D;
int done = 0;
D = CreateDeque();
while (!done) {
switch(GetOp()) {
case push:
scanf("%d", &X);
if (!Push(X, D)) printf("Memory is Full!\n");
break;
case pop:
X = Pop(D);
if ( X==ERROR ) printf("Deque is Empty!\n");
break;
case inject:
scanf("%d", &X);
if (!Inject(X, D)) printf("Memory is Full!\n");
break;
case eject:
X = Eject(D);
if ( X==ERROR ) printf("Deque is Empty!\n");
break;
case end:
PrintDeque(D);
done = 1;
break;
}
}
return 0;
}