習題3.13 雙端隊列（25 分）浙大版《數據結構（第2版）》題目集

雙端隊列（deque，即double-ended queue的縮寫）是一種具有隊列和棧性質的數據結構，即可以（也只能）在線性表的兩端進行插入和刪除。若以順序存儲方式實現雙端隊列，請編寫例程實現下列操作：

• Push(X,D)：將元素X插入到雙端隊列D的頭；
• Pop(D)：刪除雙端隊列D的頭元素，並返回；
• Inject(X,D)：將元素X插入到雙端隊列D的尾部；
• Eject(D)：刪除雙端隊列D的尾部元素，並返回。

函數接口定義：

bool Push( ElementType X, Deque D );
ElementType Pop( Deque D );
bool Inject( ElementType X, Deque D );
ElementType Eject( Deque D );

其中Deque結構定義如下：

typedef int Position;
typedef struct QNode *PtrToQNode;
struct QNode {
    ElementType *Data;      /* 存儲元素的數組   */
    Position Front, Rear;   /* 隊列的頭、尾指針 */
    int MaxSize;            /* 隊列最大容量     */
};
typedef PtrToQNode Deque;

注意：Push和Inject應該在正常執行完操作后返回true，或者在出現非正常情況時返回false。當Front和Rear相等時隊列為空，Pop和Eject必須返回由裁判程序定義的ERROR。

裁判測試程序樣例：

#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;      /* 存儲元素的數組   */
    Position Front, Rear;   /* 隊列的頭、尾指針 */
    int MaxSize;            /* 隊列最大容量     */
};
typedef PtrToQNode Deque; 

Deque CreateDeque( int MaxSize )
{   /* 注意：為區分空隊列和滿隊列，需要多開辟一個空間 */
    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();          /* 裁判實現，細節不表 */
void PrintDeque( Deque D ); /* 裁判實現，細節不表 */

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;
}

/* 你的代碼將被嵌在這里 */

輸入樣例：

3
Pop
Inject 1
Pop
Eject
Push 2
Push 3
Eject
Inject 4
Inject 5
Inject 6
Push 7
Pop
End

輸出樣例：

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


樣例沒啥用，編譯器編譯過不了所以就干寫了四個函數，要注意尾指針需要減一。

代碼：

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;
}