So I want to split each digit of a decimal number into an array. I have the following code:

#include <stdio.h>
int * splitNumberIntoArr(int num) {

    int i = num;
    int modulus,newNum;
    static int arr[5];
    int j = 0;

    while (i > 0) {
        modulus = i % 10;
        newNum = i / 10;
        arr[j] = modulus;
        j  ;
        i = newNum;
    };

    return arr;
};

int main() {
    int num;
    printf("Provide a number:\t");
    scanf("%d", &num);   

    int *arr;
    arr = splitNumberIntoArr(num);

    int k;
    for(k = 0; k <= sizeof(arr) / sizeof(arr[0]); k  ) {
        printf("%d\n",arr[k]);
    
    return 0;
};

When num is an integer consising of 3 digits, the code works how it is supposed to.

However, when the input consists of more than 3 digits, the array that is returned by the splitNumberIntoArr()

function only returns an array of length 2.

for example,

Since I am new to C, I struggle to understand why this problem even exists, taking into consideration the fact that the declared array is of length 5: static int arr[5];

Your help would be greatly appreciated.

CodePudding user response：

Try something like this:

#include <stdio.h>
#include <string.h> // for memset

void splitNumberIntoArr(int num, int *arr) {

    int i = num;
    int modulus, newNum;
    int j = 0;

    while (i > 0) {
        modulus = i % 10;
        newNum = i / 10;
        arr[j] = modulus;
        j  ;
        i = newNum;
    };
}

int main() {
    int num;
    scanf("%d", &num);

    int arr[32];
    memset(arr, -1, sizeof(arr));
    splitNumberIntoArr(num, arr);

    for (int k = 0; k < sizeof(arr) / sizeof(arr[0]) && arr[k] != -1; k  ) {
        printf("%d\n",arr[k]);
    }
}

In main(), the sizeof(arr) is known, because it lies on the stack.