如何将多个整数放入 int* 选项卡； 在两个不同的循环中，用 0 分隔，例如。 [1,1,1,0,1,1] 在 VS 2019 中 C

Question

I am writing a emulator for Turing machine subtraction and, to start, I need to have the m and n converted into 1s and one 0s. For example, if m = 3 , n = 2 , the output would be [1,1,1,0,1,1] in the int array.

I tried using malloc to allocate memory for int* tab and, after that, I simply put the first ones in the first loop, then append a 0, then, in another loop, I'm adding the n 1s.

The problem is with Visual Studio, I think, because I tried the same code in vim and the output was correct. In VS, the output of 1s is correct but, instead of 0, I get some random negative number.

Here's the code:

    scanf_s("%d", &m);
    printf("n = ");
    scanf_s("%d", &n);
    int* tab = malloc(sizeof(int) * (n + m + 1));
    int i;
    for (i = 0; i < m; i++)
    {
        tab[i] = 1;
    }
    tab[i + 1] = 0;
    int j = 0;
    for (j = i + 1; j < n + i + 1; j++)
    {
        tab[j] = 1;
    }

    for (int k = 0; k < n + m + 1; k++)
    {
        printf("%d", tab[k]);
    }

The bad output from VS

Answer 1

I believe

 tab[i + 1] = 0;

is the problem. From previous loop execution the control will only come out when i<m is false, ie, for the case when i == m , as per the increment statement.

Now, you want to put the 0 at this index, not at index + 1 .

Change to tab[i] = 0; .

Now, the probable reason for the negative number: The content of the memory location returned by malloc() is indeterminate, so if you miss to write the index when i == m (you were writing from 0 to m-1 , then from m+1 to m+n-1 ), while reading it'll return that indeterminate value.

Answer 2

The problem is in your tab[i + 1] = 0; line. When the preceding loop has finished, then i will be equal to m — that is to say, the i value will already be "one beyond the end".

So, just change that to: tab[i] = 0; and you should be fine.