Why doesn't the count integer return the expected value of d? as in digit?

Question

I'm working on a coding problem from code-wars and I'm having trouble computing the right answer that it expects from the test values as well as the example tests that they give you! Here is the prompt: "Take an integer n (n >= 0) and a digit d (0 <= d <= 9) as an integer. Square all numbers k (0 <= k <= n) between 0 and n. Count the numbers of digits d used in the writing of all the k**2. Call nb_dig (or nbDig or ...) the function taking n and d as parameters and returning this count."

#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include<array>
#include<assert.h>
#include<fstream>
using namespace std;

class CountDig
{
public:
    static int nbDig(int n, int d);
};

int CountDig::nbDig(int n, int d)
{
    int count = 0;
    for (int i = 0; i < n; i++)
    {
        int j = i;
        while (j > 0)
        {
            if (j % 10 == d)
                count++;
            j /= 10;
        }
    }
    return count;
}
int main()
{
    CountDig cnt;
    //count.nbDig();
    cout << cnt.nbDig(10, 1) << endl;
    system("PAUSE");
    return 0;
}

And one of the examples used for the parameters n and d are nbDig(10,1) and nbDig(25,1).For nbDig(10,1) the expected answer is supposed to be 4 and for nbDig(25,1) it's supposed to be 11.

Answer 1

int countDigit( int num, int digit ) {
    if( num == 0 && digit == 0 ) return 1; // special case initial condition for 0 and 0
    int count = 0;

    int j = i;
    while (j > 0)
    {
        if (j % 10 == d)
            count++;
        j /= 10;
    }
  return count;
}