Add an element that is not in the array

Question

I’m new to C, I’ve been trying to find a way to do this program but always returns a result that I can’t understand when printing the array for visualization. Example of entered values: 1,1,2,3,4,4,5,6 (99 to stop the program) I would like this to be the output: 1,2,3,4,5,6 But this returns: -1,6,40,0,4203721,0,3,0 Is there any simpler way to do this?

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

int main() 
{
  int valor,vet[10],i;
  while(1)
  {
    printf("valor:");
    scanf("%d",&valor);
    if(valor==99)
    {
      break;
    }
    int c=0;
    for(i=0;i<10;i++)
    {

      if(vet[1]==valor)
      {
        c++;
      }
    }
    int cc=0;
    if(c==0)
    {
        for(i=0;i<10;i++)
        {
            cc++;
        }
        vet[cc] = valor;
    }

    }



  for (i=0; i < 10; i++)
  {
    printf("%d ", vet[i]);
  }
  return 0;
}

Answer 1

Let’s start with what’s not right.

Here you got it wrong and used 1 instead of i:

if(vet[1]==valor)
{
    c++;
}

Further down did a for that is not useful:

int cc=0;
if(c==0)
{
    for(i=0;i<10;i++)
    {
        cc++;
    }
    vet[cc] = valor;
}

Note that you are always counting the same amount of elements in for, which are 10. Regardless of the values that are there and add the element in an invalid position, outside the array. Instead you want to add from the top, and increase one unit each time you insert.

Let’s correct these two points I mentioned, keeping the code as close to what I had:

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

int main() {
    int valor,vet[10],i, ultima_posicao = 0; //variavel para ultima posicao começa a 0
    while(1) {
        printf("valor:");
        scanf("%d",&valor);
        if(valor==99) {
            break;
        }
        int c=0;
        for(i=0; i<10; i++) {
            if(vet[i]==valor) {
                c++;
            }
        }

        if(c==0) {
            vet[ultima_posicao++] = valor; //apenas isto para inserir o valor
        }
    }

    for (i=0; i < ultima_posicao; i++) { //mostra só até os que inseriu
        printf("%d ", vet[i]);
    }
    return 0;
}

The instruction vet[ultima_posicao++] = valor; allows you to put the value in the right position, and increases it so that in the next insertion it is also in the correct location.

Personally I think it is much more organized, if you create a function to check if the value exists in the array. And it makes it easier even at the logical level, since it doesn’t even have to count, and it can do return straightforward:

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

int existe(int vet[10], int valor) {
    int i;
    for(i=0; i<10; i++) {
        if(vet[i]==valor) {
            return 1;
        }
    }
    return 0;
}

int main() {
    int valor,vet[10],i, ultima_posicao = 0;
    while(1) {
        printf("valor:");
        scanf("%d",&valor);
        if(valor==99) {
            break;
        }
        if(!existe(vet, valor)) {
            vet[ultima_posicao++] = valor;
        }
    }

    for (i=0; i < ultima_posicao; i++) {
        printf("%d ", vet[i]);
    }
    return 0;
}

Check it out at Ideone

I didn’t put it here in the answer, but it is useful to also prevent the user from entering more values than the size of the array. You can do this by testing if the variable ultima_posicao has a value of 10 or more, in which case the program ends.