Difficulties with Arrays

Question

Hello, Good Afternoon. I am a computer student and I am having difficulties with a part of a code, which is for the delivery of a work of my course.

void criar_cliente()
{
        /// Número do dia do aniversario, será armazenado como o id do usuário.    
        int id, j = 0;
        printf ("\nInsira o dia do seu aniversario: ");
        scanf ("%d", &id);

        /// Se acaso houver um id já presente no vetor, o programa informa esse erro para o usuário.
        if (id == clientes[j])
        {
            printf ("\n***Este Cliente já existe!***\n\n");
        }

        ///Se o id não tiver presente no vetor, o programa vai criar um novo cliente.
        else
        {
            j = j + 2;
            clientes [j] = id;
            printf ("\n\nCliente Criado com Sucesso!!!");
            printf ("\n***O numero digitado será o seu identificador. Portanto não o esqueça!\n\n\n\n\n\n");
        }
}

Client[ j ] is a vector that has 50 positions. This code is inside the "void creat_client()".

When I type a value, e.g.: 20, it stores in the first vector, when I type this value again, the program says that this number already exists. So far, the program meets the proposal I want. The problem is when I type a new value, e.g.: 3, instead of the program jumping to the next vector position, it updates the old value by putting 3 in its place.

Someone could help me with this code, I’m having it for a long time, and so far I haven’t found a solution. Thanks in advance.

Answer 1

The problem with your code is in the if part. Note that when the function starts the value of j is 0, then ALWAYS the comparison of if will be:

if(id == clientes[0])

Then the id value will only be compared to at the first position if the age is in client[1] the program will not compare with that id.

The problem about writing is that it will always put the new value at the j+2 position, as j ALWAYS will be 0 so the value will always be 0+2:

0 = 0 + 2;

The above operation is always done and the result will always be 2 and so your program on writes

A simple solution is to do a for to traverse the vector:

for(j = 0; j < 50; j++)
{
    if(id == cliente[j])
    {
        printf("Cliente já existe!");
    }
    else
    {
        clientes [j] = id;
        printf ("\n\nCliente Criado com Sucesso!!!");
        break;
    }
}

The above code will solve your problem, note that if will now compare to all positions within the client until it finds a location where the entered id does not exist, when this occurs then Else is activated and the id is stored at the position, the break serves to exit the loop prematurely. The above code will still have some errors in the future if you delete some client, the solution for this would be to sort the array, but this is already subject to another topic.