双端队列(deque,即double-ended queue的缩写)是一种具有队列和栈性质的数据结构,即可以(也只能)在线性表的两端进行插入和删除。若以顺序存储方式实现双端队列,请编写例程实现下列操作:
-
Push(X,D)
:将元素X
插入到双端队列D
的头; -
Pop(D)
:删除双端队列D
的头元素,并返回; -
Inject(X,D)
:将元素X
插入到双端队列D
的尾部; -
Eject(D)
:删除双端队列D
的尾部元素,并返回。
函数接口定义:
bool Push( ElementType X, Deque D );
ElementType Pop( Deque D );
bool Inject( ElementType X, Deque D );
ElementType Eject( Deque D );
其中Deque
结构定义如下:
typedef int Position;
typedef struct QNode *PtrToQNode;
struct QNode {
ElementType *Data; /* 存储元素的数组 */
Position Front, Rear; /* 队列的头、尾指针 */
int MaxSize; /* 队列最大容量 */
};
typedef PtrToQNode Deque;
注意:Push
和Inject
应该在正常执行完操作后返回true,或者在出现非正常情况时返回false。当Front
和Rear
相等时队列为空,Pop
和Eject
必须返回由裁判程序定义的ERROR
。
裁判测试程序样例:
#include <stdio.h>
#include <stdlib.h>
#define ERROR -1
typedef int ElementType;
typedef enum { push, pop, inject, eject, end } Operation;
typedef enum { false, true } bool;
typedef int Position;
typedef struct QNode *PtrToQNode;
struct QNode {
ElementType *Data; /* 存储元素的数组 */
Position Front, Rear; /* 队列的头、尾指针 */
int MaxSize; /* 队列最大容量 */
};
typedef PtrToQNode Deque;
Deque CreateDeque( int MaxSize )
{ /* 注意:为区分空队列和满队列,需要多开辟一个空间 */
Deque D = (Deque)malloc(sizeof(struct QNode));
MaxSize++;
D->Data = (ElementType *)malloc(MaxSize * sizeof(ElementType));
D->Front = D->Rear = 0;
D->MaxSize = MaxSize;
return D;
}
bool Push( ElementType X, Deque D );
ElementType Pop( Deque D );
bool Inject( ElementType X, Deque D );
ElementType Eject( Deque D );
Operation GetOp(); /* 裁判实现,细节不表 */
void PrintDeque( Deque D ); /* 裁判实现,细节不表 */
int main()
{
ElementType X;
Deque D;
int N, done = 0;
scanf("%d", &N);
D = CreateDeque(N);
while (!done) {
switch(GetOp()) {
case push:
scanf("%d", &X);
if (!Push(X, D)) printf("Deque is Full!\n");
break;
case pop:
X = Pop(D);
if ( X==ERROR ) printf("Deque is Empty!\n");
else printf("%d is out\n", X);
break;
case inject:
scanf("%d", &X);
if (!Inject(X, D)) printf("Deque is Full!\n");
break;
case eject:
X = Eject(D);
if ( X==ERROR ) printf("Deque is Empty!\n");
else printf("%d is out\n", X);
break;
case end:
PrintDeque(D);
done = 1;
break;
}
}
return 0;
}
/* 你的代码将被嵌在这里 */
输入样例:
3
Pop
Inject 1
Pop
Eject
Push 2
Push 3
Eject
Inject 4
Inject 5
Inject 6
Push 7
Pop
End
输出样例:
Deque is Empty!
1 is out
Deque is Empty!
2 is out
Deque is Full!
Deque is Full!
3 is out
Inside Deque: 4 5
样例没啥用,编译器编译过不了所以就干写了四个函数,要注意尾指针需要减一。
代码:
bool Push( ElementType X, Deque D )
{
if((D->Rear - D->Front + D->MaxSize)%D->MaxSize != D->MaxSize - 1)
{
D->Front = (D->Front - 1 + D->MaxSize)%D->MaxSize;
D->Data[D->Front] = X;
}
else return false;
return true;
}
ElementType Pop( Deque D )
{
if(D->Rear != D->Front)
{
ElementType a = D->Data[D->Front];
D->Front = (D->Front + 1)%D->MaxSize;
return a;
}
else return ERROR;
}
bool Inject( ElementType X, Deque D )
{
if((D->Rear - D->Front + D->MaxSize)%D->MaxSize != D->MaxSize - 1)
{
D->Data[D->Rear] = X;
D->Rear = (D->Rear + 1)%D->MaxSize;
}
else return false;
return true;
}
ElementType Eject( Deque D )
{
if(D->Rear != D->Front)
{
D->Rear = (D->Rear - 1 + D->MaxSize)%D->MaxSize;
ElementType a = D->Data[D->Rear];
return a;
}
else return ERROR;
}