queue1.c

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


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

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

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

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

bool push(Queue* 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(Queue* 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 front(Queue* q)
{
    if (empty(q))
        return -1;
    return q->buffer[q->front];
}

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

int main(void)
{
    Queue q = {NULL, 0, 0, 0, 0};
    int N = 5;
    int i;
    q.buffer = (int*)malloc(sizeof(int) * N);
    q.size = N;

    for(i = 0; i < 10; i++)
    {
        push(&q, i);
        printf("%d %d %d | %d %d %d\n", i, q.front, q.back, front(&q), back(&q), size(&q));
    }

    for(i = 0; i < 20; i++)
    {
        pop(&q);
        printf("%d %d %d | %d %d %d\n", i, q.front, q.back, front(&q), back(&q), size(&q));
        push(&q, 10 + i);
    }
    free(q.buffer);

    return 0;
}