3.4 双端队列

#include <stdio.h>
#include <stdlib.h>

#define ERROR 1e5

typedef struct Node {
    int Element;
    struct Node *next, *last;
}*PtrToNode;

typedef struct DequeRecord {
    struct Node *front, *rear;
}*Deque;

typedef enum { push, pop, inject, eject, disp, end } Operation;
 
Deque CreateDeque(){
    Deque deque = (Deque)malloc(sizeof(struct DequeRecord));
    PtrToNode temp = (PtrToNode)malloc(sizeof(struct Node));
    temp->last = NULL;
    temp->next = NULL;
    deque->front = temp;
    deque->rear = temp;
    return deque;
 
}
 
int Push(int X, Deque D)
{
    PtrToNode temp;
    temp = (PtrToNode)malloc(sizeof(struct Node));
    if (!temp)
        return 0;
    temp->Element = X;
    // 空队列情况
    if (D->front == D->rear){
        D->front->next = temp;
        temp->last = D->front;
        temp->next = NULL;
        D->rear = temp;
        return 1;
    }
    // 一般情况
    temp->next = D->front->next;
    temp->last = D->front;
    D->front->next->last = temp;
    D->front->next = temp;
    return 1;
}
 
int Pop(Deque D){
    PtrToNode temp;
    int X;
    // 空队列
    if (D->front == D->rear)
        return ERROR;
 
    temp = D->front->next;
    X = temp->Element;
    // 如果只有一个节点的情况
    if (D->front->next == D->rear){
        D->rear = D->front;
        D->rear->next = NULL;
        free(temp);
        return X;
    }
    // 一般情况
    temp->next->last = D->front;
    D->front->next = temp->next;
    free(temp);
    return X;
}
 
// 末尾添加一个元素
int Inject(int X, Deque D){
    PtrToNode temp;
    temp = (PtrToNode)malloc(sizeof(struct Node));
    if (!temp)
        return 0;
    temp->Element = X;
    // 空队列
    if (D->front == D->rear){
        D->front->next = temp;
        temp->last = D->front;
        D->rear = temp;
        return 1;
    }
    D->rear->next = temp;
    temp->next = NULL;
    temp->last = D->rear;
    D->rear = temp;
    return 1;
}
 
// 从末尾移除一个元素
int Eject(Deque D){
    PtrToNode temp;
    int X;
    if (D->front == D->rear)
        return ERROR;
 
    temp = D->rear;
    X = temp->Element;
    D->rear = temp->last;
    D->rear->next = NULL;
    free(temp);
    return X;
}

Operation GetOp(){
    int op;
    puts("请输入操作码：1 左入队，2 左出队，3 右入队，4 右出队，5 显示队列，6 退出");
    scanf("%d",&op);
    switch(op){
        case 1:return push;
        case 2:return pop;
        case 3:return inject;
        case 4:return eject;
        case 5:return disp;
        case 6:return end;
        default:exit(1);
    }
}

// 左边front，右边rear，next指向右,带头节点
void PrintDeque(Deque D){
    PtrToNode p1;
    p1=D->front->next;          // 头节点，front所指单元的next域
    printf("队列中剩余元素：");
    while(p1!=D->rear->next){
        printf("%d ",p1->Element);
        p1=p1->next;
    }
    printf("
");
}     

// 该双端队列可在两端进行入队和出队操作，在左边进行操作的时候要考虑头节点

int main(){
    int e;
    Deque D;
    int done = 0;
 
    D = CreateDeque();
    while (!done) {
        switch(GetOp()) {
        case push:
            puts("push:");
            scanf("%d", &e);
            if (!Push(e, D)) printf("Memory is Full!
");
            break;
        case pop:
            e = Pop(D);
            if ( e==ERROR ) printf("Deque is Empty!
");
            break;
        case inject: 
            puts("inject:");
            scanf("%d", &e);
            if (!Inject(e, D)) printf("Memory is Full!
");
            break;
        case eject:
            e = Eject(D);
            if ( e==ERROR ) printf("Deque is Empty!
");
            break;
        case disp:
            PrintDeque(D);
            break;
        case end:
            done = 1;
            break;
        }
    }
    return 0;
}