fila_prioriade.c

#include <stdio.h>

int main(void) {
    typedef struct {
        char vet[3];
        int front,rear;
    } tfila;

    void create(tfila *f){
        f->front = 0;
        f->rear = 0;
    }

    int next(int n){
        if(n < 3)
            return n + 1;
        return 0;
    }

    int isempty(tfila f){
        return f.front == f.rear;
    }
    
    int isfull(tfila f){
        return next(f.rear) == f.front;
    }

    void store(tfila *f, char elem){
        if(isfull(*f))
            printf("\noverflow\n");
        else{
            f->vet[f->rear] = elem;
            f->rear = next(f->rear);
        }
    }

    char retrieve(tfila *f){
        if(isempty(*f))
            printf("\nunderflow\n");
        else{
            char aux = f->vet[f->front];
            f->front = next(f->front);
            return aux;
        }        
    }

    typedef struct {
        tfila f1, f2, f3, f4;
    } tfilaprior;

    void init(tfilaprior *fp){
        create(&(fp->f1));
        create(&(fp->f2));
        create(&(fp->f3));
        create(&(fp->f4));
    }

    void inclui(tfilaprior *fp, int prior, char elem){
        switch(prior) {
            case 1 :
                store(&(fp->f1), elem);
                break;
            case 2 :
                store(&(fp->f2), elem);
                break;
            case 3 :
                store(&(fp->f3), elem);
                break;
            case 4 :
                store(&(fp->f4), elem);
                break;
        }
    }

    char atende(tfilaprior *fp){
        if(!isempty(fp->f1))
            return retrieve(&fp->f1);
        if(!isempty(fp->f2))
            return retrieve(&fp->f2);
        if(!isempty(fp->f3))
            return retrieve(&fp->f3);
        return retrieve(&fp->f4);
    }

    tfilaprior filaprior;
    init(&filaprior);

    inclui(&filaprior, 1, 'a');
    inclui(&filaprior, 2, 'b');
    inclui(&filaprior, 2, 'c');
    inclui(&filaprior, 3, 'd');
    inclui(&filaprior, 4, 'e');

    printf("%c\n", atende(&filaprior));
    printf("%c\n", atende(&filaprior));
    printf("%c\n", atende(&filaprior));
    printf("%c\n", atende(&filaprior));
    printf("%c\n", atende(&filaprior));
}