LinearQueue.c

#include <stdio.h>
#include <stdlib.h>
#define QUEUE_SIZE 10

typedef char element;
typedef struct {
    element queue[QUEUE_SIZE];
    int front, rear;
} QueueType;

QueueType* createQueue() {
    QueueType* Q;
    Q = (QueueType*)malloc(sizeof(QueueType));
    Q -> front = -1;
    Q -> rear = -1;
    return Q;
}

int isEmpty(QueueType* Q) {
    return Q -> front == Q -> rear;
}

int isFull(QueueType* Q) {
    return Q -> rear == QUEUE_SIZE - 1;
}

void enQueue(QueueType* Q, element item) {
    if(isFull(Q)) exit(0);
    Q -> rear++;
    Q -> queue[Q -> rear] = item;
}

element deQueue(QueueType* Q) {
    if(isEmpty(Q)) exit(0);
    Q -> front++;
    return Q -> queue[Q -> front];
}

element peek(QueueType* Q) {
    if(isEmpty(Q)) exit(0);
    return Q -> queue[Q -> front + 1];
}

void print(QueueType* Q) {
    printf("Queue: {");
    int i = Q -> front + 1;
    for(; i <= Q -> rear; ++i) {
        printf("%3c", Q -> queue[i]);
    }
    printf("  }\n");
}

int main() {
    QueueType* Q = createQueue();
    
    printf("A -> EnQueue\n");
    enQueue(Q, 'A');
    print(Q);
    
    printf("B -> EnQueue\n");
    enQueue(Q, 'B');
    print(Q);
    
    printf("C -> EnQueue\n");
    enQueue(Q, 'C');
    print(Q);
    
    printf("Peek -> %c\n", peek(Q));
    
    printf("DeQueue -> %c\n", deQueue(Q));
    print(Q);

    printf("DeQueue -> %c\n", deQueue(Q));
    print(Q);
    return 0;
}