원형 큐(Circular Queue)

element 한 자리가 항상 비게되지만, 재정렬 없이 큐 이용이 가능하다.

First In First Out(FIFO) 구조

#include <stdio.h>

#define MAX_Q_SIZE 11	// 원형 큐 이용 가능 크기 MAX_SIZE - 1

typedef enum eSelectMenu {
	selectAdd = 1,
	selectDelete,
	selectPrint,
	selectExit
} eSelectMenu;

typedef enum eBool {
	false,
	true
} eBool;

void Add(int [], int*, int*, int);
int Delete(int [], int*, int*);
eBool IsEmpty(int, int);
eBool IsFull(int, int);

int main(void) {
	int queue[MAX_Q_SIZE];
	int rear, front, data, i;
	eSelectMenu select;

	if (MAX_Q_SIZE < 2) {
		fprintf(stderr, "Queue size error\n");
		return 0;
	}
	else {
		rear = 0;
		front = 0;
	}

	while (1) {
		printf("1. add / 2. delete / 3. print / 4. exit\n");
		printf("select: ");
		scanf_s("%d", &select);
		switch (select) {
		case selectAdd:
			if (IsFull(front, rear) == true) {
				printf("Queue Full\n\n");
				break;
			}
			printf("data: ");
			scanf_s("%d", &data);
			Add(queue, &front, &rear, data);
			printf("\n");
			break;
		case selectDelete:
			if (IsEmpty(front, rear) == true) {
				printf("Queue Empty\n\n");
				break;
			}
			printf("return data: %d\n\n", Delete(queue, &front, &rear));
			break;
		case selectPrint:
			printf("\n< Print >\n");
			printf("front: %d, rear: %d\n", front, rear);
			if (IsEmpty(front, rear) == true)
				printf("Qeueu Empty");
			else {
				for (i = (front + 1) % MAX_Q_SIZE; i != (rear + 1) % MAX_Q_SIZE; i = (i + 1) % MAX_Q_SIZE)
					printf("%d ", queue[i]);
			}
			printf("\n\n");
			break;
		case selectExit:
			printf("Exit Program\n");
			return 0;
		default:
			printf("re\n\n");
		}
		while (getchar() != '\n') {}
	}
}

void Add(int queue[], int * front, int * rear, int data) {
	*rear = (*rear + 1) % MAX_Q_SIZE;
	queue[*rear] = data;
}

int Delete(int queue[], int * front, int * rear) {
	int data;
	*front = (*front + 1) % MAX_Q_SIZE;
	data = queue[*front];
	return data;
}

eBool IsFull(int front, int rear) {
	return (rear + 1) % MAX_Q_SIZE == front ? true : false;
}

eBool IsEmpty(int front, int rear) {
	return rear == front ? true : false;
}