Delete a struct record using free()

Question

I’m creating a record using struct, where I must have a menu to include, show and attend (exclude) patients.

The problem is in the exclusion function that because of my lack of knowledge I do not understand what would be the correct way to accomplish. I thought to use the free() but by dealing directly with memory I’m not sure if it would work in all cases.

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

    char menu(){
        fflush (stdin);
        printf ("\n\t\t-----Menu-----");
        printf ("\n\t\t 1 Incluir Paciente");
        printf ("\n\t\t 2 Mostrar Pacientes");  
        printf ("\n\t\t 3 Atender Paciente");   
        printf ("\n\t\t 0 Sair");
        char op = getch();
        system ("cls");
        return op;
    }

    typedef struct paciente{
        char nome [20], matricula [6], senha[6], atendimento[50];
        struct paciente *prox;
    }pacienteat;

    pacienteat *ini, *aux;

    void inicio(){
        ini= NULL;
    }

    int estaVazia(){
        return (ini==NULL);
    }

    void inserir (){
        int senha=1;

        aux=(pacienteat*) malloc(sizeof(pacienteat));
        printf("\nInforme o numero do atendimento");
        fflush(stdin);
        gets(aux->atendimento);

        printf ("\nInforme o nome do paciente: ");
        fflush (stdin);
        gets (aux->nome);

        printf ("\nInforme o numero da matricula: ");
        fflush (stdin);
        gets (aux->matricula);

        printf ("\nInforme a senha atendimento: ");
        fflush (stdin);
        gets (aux->senha);;

        aux->prox = ini;
        ini = aux;
    }

    void listar(){  
        for (aux = ini; aux != NULL; aux = aux->prox){
            printf("\nNome: %s - Matricula: %s - Atendimento: %s - Senha: %s", aux->nome, aux->matricula, aux->atendimento, aux->senha);
        }
    }

    void excluir(){
        int n_remover;
        listar();
        printf("Digite o numero de quem voce quer remover");
        scanf("%d",&n_remover);
        aux[n_remover] = aux[aux->atendimento-1]; 
        atendimento--; 
        aux = (pacienteat*) realloc(pacienteat,num*sizeof(pacienteat));
    }
    int main(){
        inicio();
        int x=0,nn;

        char op=menu();
        while(op != '0'){
            switch (op){
                case'1':
                    inserir();
                    break;
                case'2':
                    listar();
                    break;
                case'3':
                    excluir();
                    break;
            }
            op = menu();
        }
        system("pause");
    }

Answer 1

For an exercise code this is good, but know that in real code it would be something quite different from that. Some things in this code work by coincidence, in certain situations will not work.

Since you are using a linked list you have no reason to relocate. You should only use free(). It has to be given at the address of the list item. And then the previous element should receive the address of the element that was pointed out in the element that is being removed, which can be up to 0.

The aux[n_remover] doesn’t make sense because you don’t have one array, not even through a stable, linear pointer.

I have no idea what it is atendimento--, the impression that he chose something random and threw in the code.

I’m afraid of that aux, looks like Ambi in the thick and I doubt that this is working other than in a very naive test.

When several errors is difficult to find a solution, because you will have to solve all until it works.