循环队列

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

#define ERROR 0
#define OK 1

typedef struct Queue {
    int *data;
    int head, tail, length, count;
}Queue;

void init(Queue *q, int length) {
    q->data = (int *)malloc(sizeof(int) * length);
    q->length = length;
    q->head = 0;
    q->tail = -1;
    q->count = 0;
}

int push(Queue *q, int element) {
    if (q->count >= q->length) {
        return ERROR;
    }
    q->tail = (q->tail + 1) % q->length;
    q->data[q->tail] = element;
    q->count++;
    return OK;
}

void output(Queue *q) {
    int i = q->head;
    do {
        printf("%d ", q->data[i]);
        i = (i + 1) % q->length;
    } while(i != (q->tail + 1) % q->length);
    printf("\n");
}

int front(Queue *q) {
    return q->data[q->head];
}

void pop(Queue *q) {
    q->head = (q->head + 1) % q->length;
    q->count--;
}

int empty(Queue *q) {
    return q->count == 0;
}

void clear(Queue *q) {
    free(q->data);
    free(q);
}

int main() {
    Queue *q = (Queue *)malloc(sizeof(Queue));
    init(q, 100);
    for (int i = 1; i <= 10; i++) {
        push(q, i);
    }
    output(q);
    if (!empty(q)) {
        printf("%d\n", front(q));
        pop(q);        
    }
    output(q);
    clear(q);
    return 0;
}