Question

printf("\n\tHow many integers: ");
    scanf("%d", &num);

    iPtr = (int*) malloc(num * sizeof(int));

    for(i = 0; i < num; i++) {
        printf("Enter integer # %d ", i + 1);
        scanf("%d", (iPtr + i));

        temp = *(iPtr + i);
        while(temp != 0) {

            if(i == temp % 10) {
                ary[i]++;
            }
            temp /= 10;
        }
    }

    for(i = 0; i < 10; i++) {
        if(ary[i] > 0) {
            printf("digit %d : %d\n", i, ary[i]);
        }
    }

I am writing a program to store the occurrences of an digit from an integers,but when I run the program, I see the array is not working

so I want to ask why it is not allow me to store the digit from an integer?
and how to fix it?

and 1 more question, what is the different between if(x = y) and if(x == y)

Answer 1

Ok so you’ve almost got it right but I think the biggest issue is your array has garbage in it to begin with (when declared).

 int i, temp, num, *iPtr;
int ary[10] = {0};            //I can only assume you did *not* do this

//printf("\n\tHow many integers: ");
//scanf("%d", &num);
num = 2;

iPtr = malloc(num * sizeof(int));



for(i = 0; i < num; i++) 
{
    printf("Enter integer # %d ", i+1);
    scanf("%d", (iPtr +1));

    temp = *(iPtr+1);
    while(temp != 0) 
    {

        if( (i) == temp % 10)     
        {
            ary[i]++;             
        }

        temp /= 10;
    }
}

for(i = 0; i < 10; i++) 
{
    if(ary[i] > 0) 
    {
        printf("digit %d : %d\n", i, ary[i]);
    }
}

This program is also incomplete, because your loop might end before you’ve even checked a digit high enough to match. Ie, you’re checking if temp still has a number in it, but you’re only comparing it to i, which doesn’t change (so if the digit in temp is 9, but i is 1, you’ll never trigger to see that there’s a 9 to count).

So I modified

if( (i) == temp % 10)     
{
    ary[i]++;             
}

to

        for (int zz = 0; zz < 10; zz++)
        {
            if( (zz) == temp % 10) 
            {
               ary[zz]++;            
            }
        }

And now the program counts all the digits.
Output:

This is all assuming I’m even understanding your program right. And usually I don’t like straight posting code but I really didn’t know how else to get the point across. Tired atm. :/