LinkedQueue

#include <stdio.h>
#include <malloc.h>

typedef char element;
typedef struct DQNode{
    element data;
    struct DQNode *llink;
    struct DQNode *rlink;
}DQNode;

typedef struct{
    DQNode *front, *rear;
} DQueType;

DQueType *createDQue()
{
    DQueType *DQ;
    DQ = (DQueType *)malloc(sizeof(DQueType));
    DQ->front = NULL;
    DQ->rear = NULL;
    return DQ;
}

int isEmpty(DQueType *DQ)
{
    if (DQ->front == NULL) {
        printf("\n Linked Queue is Empty \n");
        return 1;
    }
    else return 0;
}

void insertFront(DQueType *DQ, element item)

{
    DQNode *newNode = (DQNode *)malloc(sizeof(DQNode));
    newNode->data = item;
    if (DQ->front == NULL) {
        DQ->front = newNode;
        DQ->rear = newNode;
        newNode->rlink = NULL;
        newNode->llink = NULL;
    }
    else {
        DQ->front->llink = newNode;
        newNode->rlink = DQ->front;
        newNode->llink = NULL;
        DQ->front = newNode;
    }
}

void insertRear(DQueType *DQ, element item)
{
    DQNode *newNode = (DQNode *)malloc(sizeof(DQNode));
    newNode->data = item;
    if (DQ->rear == NULL) {
        DQ->front = newNode;
        DQ->rear = newNode;
        newNode->rlink = NULL;
        newNode->llink = NULL;
    }
    else {
        DQ->rear->rlink = newNode;
        newNode->rlink = NULL;
        newNode->llink = DQ->rear;
        DQ->rear = newNode;
    }
}

element deleteFront(DQueType *DQ)
{
    DQNode *old = DQ->front;
    element item;
    if (isEmpty(DQ)) return 0;
    else {
        item = old->data;
        if (DQ->front->rlink == NULL) {
            DQ->front = NULL;
            DQ->rear = NULL;
        }
        else {
            DQ->front = DQ->front->rlink;
            DQ->front->llink = NULL;
        }
        free(old);
        return item;
    }
}

element deleteRear(DQueType *DQ)
{
    DQNode *old = DQ->rear;
    element item;
    if (isEmpty(DQ)) return 0;
    else {
        item = old->data;
        if (DQ->rear->llink == NULL) {
            DQ->front == NULL;
            DQ->rear = NULL;
        }
        else {
            DQ->rear = DQ->rear->llink;
            DQ->rear->rlink = NULL;
        }
        free(old);
        return item;
    }
}

int removeFront(DQueType *DQ)
{
    DQNode *old = DQ->front;
    if (isEmpty(DQ)) return 0;
    else if (DQ->front->rlink == NULL) {
        DQ->front = NULL;
        DQ->rear = NULL;
    }
    else {
        DQ->front = DQ->front->rlink;
        DQ->front->llink = NULL;
    }
    free(old); return 1;
}

int removeRear(DQueType *DQ)
{
    DQNode *old = DQ->rear;
    if (isEmpty(DQ)) return 0;
    else if (DQ->rear->llink == NULL) {
        DQ->front = NULL;
        DQ->rear = NULL;
    }
    else {
        DQ->rear = DQ->rear->llink;
        DQ->rear->rlink = NULL;
    }
    free(old); return 1;
}

element peekFront(DQueType *DQ)
{
    element item;
    if (isEmpty(DQ)) return 0;
    else {
        item = DQ->front->data;
        return item;
    }
}

element peekRear(DQueType *DQ)
{
    element item;
    if (isEmpty(DQ)) return 0;
    else {
        item = DQ->rear->data;
        return item;
    }
}

void printDQ(DQueType *DQ)
{
    DQNode *temp = DQ->front;
    printf("DqQue : [");
    while (temp) {
        printf("%3c", temp->data);
        temp = temp->rlink;
    }
    printf(" ] \n");
}

int main(void)
{
    DQueType *DQ1 = createDQue();
    element data;
    printf("front 삽입 A>> "); insertFront(DQ1, 'A'); printDQ(DQ1);
    printf("front 삽입 B>> "); insertFront(DQ1, 'B'); printDQ(DQ1);
    printf("rear 삽입 C>>  "); insertRear(DQ1, 'C'); printDQ(DQ1);
    printf("front 삭제  >> "); deleteFront(DQ1); printDQ(DQ1);
    printf("rear 삭제  >> "); deleteRear(DQ1); printDQ(DQ1);
    printf("rear 삽입 D>> "); insertRear(DQ1, 'D'); printDQ(DQ1);
    printf("front 삽입 E>> "); insertFront(DQ1, 'E'); printDQ(DQ1);
    printf("front 삽입 F>> "); insertFront(DQ1, 'F'); printDQ(DQ1);

    data = peekFront(DQ1); printf("peek Front item : %c \n", data);
    data = peekRear(DQ1); printf("peek Rear item : %c \n", data);

    return 0;
}