deque.c

#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <math.h>


typedef struct Deque
{
    int* buffer;
    int front;
    int back;
    int count;
    int size;
} Deque;

int size(Deque* q)
{
    return q->count;
}

bool empty(Deque* q)
{
    return size(q) == 0;
}

bool full(Deque* q)
{
    return size(q) == q->size;
}

bool push_front(Deque* q, int v)
{
    if (full(q))
        return false;

    q->front = (q->front - 1 + q->size) % q->size;
    q->buffer[q->front] = v;
    q->count++;

    return true;
}

bool push_back(Deque* q, int v)
{
    if (full(q))
        return false;

    q->buffer[q->back] = v;
    q->back = (q->back + 1) % q->size;
    q->count++;

    return true;
}

int pop_front(Deque* q)
{
    if (empty(q))
        return -1;
    q->count--;
    q->front = (q->front + 1) % q->size;
    return q->buffer[ (q->front - 1 + q->size) % q->size ];
}

int pop_back(Deque* q)
{
    if (empty(q))
        return -1;
    q->count--;
    q->back = (q->back - 1 + q->size) % q->size;
    return q->buffer[ q->back ];
}

int front(Deque* q)
{
    if (empty(q))
        return -1;
    return q->buffer[q->front];
}

int back(Deque* q)
{
    if (empty(q))
        return -1;
    return q->buffer[ (q->back - 1 + q->size) % q->size ];
}

int main(void)
{
    Deque q = {NULL, 0, 0, 0, 0};
    int N, command, v, i;

    scanf("%d", &N);

    q.buffer = (int*)malloc(sizeof(int) * N);
    q.size = N;

    while (N > 0)
    {
        scanf("%d", &command);
        switch (command)
        {
        case 1:
            scanf("%d", &v);
            push_front(&q, v);
            break;
        case 2:
            scanf("%d", &v);
            push_back(&q, v);
            break;
        case 3:
            printf("%d\n", pop_front(&q));
            break;
        case 4:
            printf("%d\n", pop_back(&q));
            break;
        case 5:
            printf("%d\n", size(&q));
            break;
        case 6:
            printf("%d\n", empty(&q));
            break;
        case 7:
            printf("%d\n", front(&q));
            break;
        case 8:
            printf("%d\n", back(&q));
            break;
        default:
            break;
        }
        N--;
    }

    free(q.buffer);

    return 0;
}