91tNkc - Online C99 Compiler & Debugging Tool

#include <stdio.h>

#define SIZE 5
int queue[SIZE];
int head, tail;

void enqueue(int value);
int dequeue(void);

int main(void)
{
    head = tail = 0;

    enqueue(1);
    enqueue(2);
    dequeue();
    enqueue(3);
    dequeue();
    enqueue(4);
    enqueue(5);
    dequeue();
    enqueue(6);

    for (int i = 0; i < SIZE; i++) {
        printf("queue[%d]=%d\n", i, queue[i]);
    }

    return 0;
}

void enqueue(int value)
{
    int next = (tail + 1) % SIZE;


    if (next == head) {
        printf("Queue is FULL. enqueue(%d) できません\n", value);
        return;
    }

    queue[tail] = value;
    tail = next;
}

int dequeue(void)
{
    if (head == tail) {
        printf("Queue is EMPTY. dequeue できません\n");
        return -1;
    }

    int data = queue[head];
    queue[head] = 0;
    head = (head + 1) % SIZE;

    return data;
}