How to read a random amount of integers in C?

Question

I need to create a way to read integers in the same input, and the amount of integers entered is random every time the program is run.

I tried to perform the following algorithm:

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

int main()
{
    long int numero, i, vetor[100000];

    i = 0;
    while(scanf("%li", &numero) != EOF)
        vetor[i++] = numero;

    while(i > 0)
        printf("%li ", vetor[i--]);

    return 0;
}

However, on one machine, 1º while never ends. And on another machine, I get a Segmentation fault. What may be happening?

Answer 1

Your problem and the use of scanf()

while(scanf("%li", &numero) != EOF)

The value that the scanf() return usually corresponds to the number of assignments performed (in your case this value is 1 because there is only one variable assignment numero).

Note that a scanf() with more than one assignment can return a lower number without being an error

chk = scanf("%d%d%d", &um, &dois, &tres);
if (chk == 3) /* 3 atribuicoes */;
if (chk == 2) /* 2 atribuicoes: `tres` nao foi atribuido */;
if (chk == 1) /* 1 atribuicao: apenas `um` foi atribuido */;
if (chk == 0) /* nenhuma atribuicao */;
if (chk == EOF) /* erro de leitura */;

In your example above you should not test the value returned by scanf() with EOF, but rather with 1

while(scanf("%li", &numero) == 1)

Answer 2

I made some small changes to your code and tested using CTRL+Z to stop reading the integers, it worked perfectly:

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

int main()
{
    long int numero, i = 0, vetor[100000];

    while(scanf("%li", &numero) != EOF)
    {
        if (i == 99999)     //caso o vetor chegue ao seu limite a leitura encerra.
        {
            printf("Limite do vetor atingido!\n");
            break;
        } 
        else 
        {
            vetor[i++] = numero;
        }
    }

    while(i > 0)
        printf("%li ", vetor[--i]);

    return 0;
}

Do the test using this code, if you give any problem let me know in the comments that I will seek to resolve it. I hope to have helped.