Count numbers having 0 as a digit

// Modified C# program to count number from 1 to n with 
// 0 as a digit.  

using System;
public class GFG{

// Returns count of integers having zero upto given digits 
static int zeroUpto(int digits) 
{ 
    // Refer below article for details 
    // https://www.geeksforgeeks.org/dsa/count-positive-integers-0-digit/ 
    int first = (int) ((Math.Pow(10,digits)-1)/9); 
    int second = (int) ((Math.Pow(9,digits)-1)/8); 
    return 9 * (first - second); 
} 

// utility function to convert character representation 
// to integer 
static int toInt(char c) 
{ 
    return (int)(c)-48; 
} 

// counts numbers having zero as digits upto a given 
// number 'num' 
static int countZero(String num) 
{ 
    // k denoted the number of digits in the number 
    int k = num.Length; 

    // Calculating the total number having zeros, 
    // which upto k-1 digits 
    int total = zeroUpto(k-1); 

    // Now let us calculate the numbers which don't have 
    // any zeros. In that k digits upto the given number 
    int non_zero = 0; 
    for (int i=0; i<num.Length; i++) 
    { 
        // If the number itself contains a zero then 
        // decrement the counter 
        if (num[i] == '0') 
        { 
            non_zero--; 
            break; 
        } 

        // Adding the number of non zero numbers that 
        // can be formed 
        non_zero += (toInt(num[i])-1) * (int)(Math.Pow(9,k-1-i)); 
    } 

    int no = 0, remaining = 0,calculatedUpto=0; 

    // Calculate the number and the remaining after 
    // ignoring the most significant digit 
    for (int i=0; i<num.Length; i++) 
    { 
        no = no*10 + (toInt(num[i])); 
        if (i != 0) 
            calculatedUpto = calculatedUpto*10 + 9; 
    } 
    remaining = no-calculatedUpto; 

    // Final answer is calculated 
    // It is calculated by subtracting 9....9 (d-1) times 
    // from no. 
    int ans = zeroUpto(k-1) + (remaining-non_zero-1); 
    return ans; 
} 

// Driver program to test the above functions 

    static public void Main() { 
        String num = "107"; 
    Console.WriteLine("Count of numbers from 1" + " to "
        + num + " is " + countZero(num)); 

    num = "1264"; 
    Console.WriteLine("Count of numbers from 1" + " to "
        + num + " is " +countZero(num)); 
    } 
} 

// This code is contributed by 29AjayKumar

using System;

class Program
{
    // Function to count the number of zeros in numbers from 1 to n (inclusive)
    static int CountZerosBruteForce(int n)
    {
        int count = 0; // Initialize count variable to 0

        // Loop through numbers 1 to n (inclusive)
        for (int i = 1; i <= n; i++)
        {
            // Convert i to string and check if it contains '0'
            if (i.ToString().Contains('0'))
            {
                count++; // Increment count if '0' is found in i
            }
        }

        return count; // Return the final count
    }

    static void Main()
    {
        int n = 107;
        Console.WriteLine(CountZerosBruteForce(n)); // Output: 17

        n = 1264;
        Console.WriteLine(CountZerosBruteForce(n)); // Output: 315
    }
}