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Count positive integers with 0 as a digit and maximum ‘d’ digits
• Difficulty Level : Easy
• Last Updated : 01 Apr, 2021

Given a number d, representing the number of digits of a number. Find the total count of positive integers which have at-least one zero in them and consist d or less digits.

Examples:
Input : d = 1
Output : 0
There's no natural number of 1 digit that contains a zero.

Input : d = 2
Output : 9

Input : d = 3
Output : 180
For d = 3, we've to count numbers from 1 to 999, that have
atleast one zero in them.
Similarly for d=4, we'd check every number from 1 to 9999. 

## We strongly recommend that you click here and practice it, before moving on to the solution.

This is mainly an extension of below post.
Count ‘d’ digit positive integers with 0 as a digit.
If we observe carefully the problem is very similar to the one which we had discussed in our first set. For a given d, we can get the required answer if we find numbers that have 0s and consist of digits 1, 2, 3….., d. Finally we can add them to get the output.
Below is the program for the same.

## C++

 // C++ program to find the count of positive integer of a// given number of digits that contain atleast one zero#includeusing namespace std; // Returns count of 'd' digit integers have 0 as a digitint findCount(int d){    return 9*(pow(10,d-1) - pow(9,d-1));} // utility function to count the required answerint findCountUpto(int d){    // Count of numbers with digits smaller than    // or equal to d.    int totalCount = 0;    for (int i=1; i<=d; i++)        totalCount += findCount(i);     return totalCount;} // Driver Codeint main(){    int d = 1;    cout << findCountUpto(d) << endl;     d = 2;    cout << findCountUpto(d) << endl;     d = 4;    cout << findCountUpto(d) << endl;    return 0;}

## Java

 // Java program to find the count of// positive integer of agiven number// of digits that contain atleast one zeroimport java.io.*;import java.math.*; class GFG {         // Returns count of 'd' digit    // integers have 0 as a digit    static int findCount(int d)    {        return 9 * (int)((Math.pow(10, d - 1)                         - Math.pow(9, d - 1)));    }         // utility function to count    // the required answer    static int findCountUpto(int d)    {        // Count of numbers with digits        // smaller than or equal to d.        int totalCount = 0;        for (int i = 1; i <= d; i++)            totalCount += findCount(i);             return totalCount;    }         // Driver Code    public static void main(String args[])    {        int d = 1;        System.out.println(findCountUpto(d));             d = 2;        System.out.println( findCountUpto(d) );             d = 4;        System.out.println(findCountUpto(d));    }}  /*This code is contributed by Nikita Tiwari.*/

## Python3

 # Python 3 program to find the# count of natural numbers upto a# given number of digits that# contain atleast one zeroimport math  # Utility function to calculate# the count of natural numbers# upto a given number of digits# that contain atleast one zerodef findCountUpto(d) :    # Sum of two GP series    GP1_Sum = 9*((int)((math.pow(10,d))-1)//9)    GP2_Sum = 9*((int)((math.pow(9,d))-1)//8)      return GP1_Sum - GP2_Sum  # Driver Coded = 1print(findCountUpto(d)) d = 2print(findCountUpto(d)) d = 4print(findCountUpto(d))  # This code is contributed by Nikita Tiwari.

## C#

 // C# program to find the count of// positive integer of agiven number// of digits that contain atleast// one zerousing System; class GFG {         // Returns count of 'd' digit    // integers have 0 as a digit    static int findCount(int d)    {        return 9 * (int)((Math.Pow(10, d - 1)                        - Math.Pow(9, d - 1)));    }         // utility function to count    // the required answer    static int findCountUpto(int d)    {        // Count of numbers with digits        // smaller than or equal to d.        int totalCount = 0;        for (int i = 1; i <= d; i++)            totalCount += findCount(i);             return totalCount;    }         // Driver Code    public static void Main()    {        int d = 1;        Console.WriteLine(findCountUpto(d));             d = 2;        Console.WriteLine( findCountUpto(d) );             d = 4;        Console.WriteLine(findCountUpto(d));    }} // This code is contributed by Sam007

## PHP

 

## Javascript

 

Output :

0
9
2619 

Time Complexity : O(d)
Auxiliary Space : O(1)
Can we make the solution more efficient ?
Yes, if we see closely, the required answer is obtained using the sum of following two Geometric Progressions:

i'th term of G.P. 1 = 9*10i - 1  where 1 <= i <= d
i'th term of G.P. 2 = 9*9i - 1 where 1 <= i <= d
The final answer is nothing but, Sum of G.P 1 = 9*(10d - 1)/(10-1)
= 9*(10d - 1)/9
Similarly,
Sum of G.P 2 = 9*(9d - 1)/(9-1)
= 9*(9d - 1)/8
Using the above facts, we can optimize the solution to run in O(1) 

Below is an efficient program for the same.

## C++

 // C++ program to find the count of natural numbers upto a// given number of digits that contain atleast one zero#includeusing namespace std; // Utility function to calculate the count of natural numbers// upto a given number of digits that contain atleast one zeroint findCountUpto(int d){    // Sum of two GP series    int GP1_Sum = 9*((pow(10,d)-1)/9);    int GP2_Sum = 9*((pow(9,d)-1)/8);     return GP1_Sum - GP2_Sum;} // Driver Codeint main(){    int d = 1;    cout << findCountUpto(d) << endl;     d = 2;    cout << findCountUpto(d) << endl;     d = 4;    cout << findCountUpto(d) << endl;    return 0;}

## Java

 // Java program to find the count// of natural numbers upto a// given number of digits// that contain atleast one zeroimport java.io.*;import java.math.*; class GFG {         // Utility function to calculate    // the count of natural numbers    // upto a given number of digits    // that contain atleast one zero    static int findCountUpto(int d)    {        // Sum of two GP series        int GP1_Sum = 9 * ((int)((Math.pow(10, d)) - 1) / 9);        int GP2_Sum = 9 * ((int)((Math.pow(9, d)) - 1) / 8);             return GP1_Sum - GP2_Sum;    }         // Driver Code    public static void main(String args[])    {        int d = 1;        System.out.println(findCountUpto(d));                 d = 2;        System.out.println(findCountUpto(d));                 d = 4;        System.out.println(findCountUpto(d));             }}  /* This code is contributed by Nikita Tiwari.*/

## Python3

 # Python 3 program to find the# count of positive integer of a# given number of digits that# contain atleast one zeroimport math # Returns count of 'd' digit# integers have 0 as a digitdef findCount(d) :    return 9*(pow(10,d-1) - pow(9,d-1));  # utility function to count# the required answerdef findCountUpto(d) :     # Count of numbers with    # digits smaller than    # or equal to d.    totalCount = 0    for i in range(1,d+1) :        totalCount = totalCount + findCount(i)      return totalCount   # Driver Coded = 1print(findCountUpto(d)) d = 2print(findCountUpto(d)) d = 4print(findCountUpto(d))  # This code is contributed by Nikita Tiwari.

## C#

 // C# program to find the count// of natural numbers upto a// given number of digits// that contain atleast one zerousing System; class GFG {         // Utility function to calculate    // the count of natural numbers    // upto a given number of digits    // that contain atleast one zero    static int findCountUpto(int d)    {                 // Sum of two GP series        int GP1_Sum = 9 * ((int)((Math.Pow(10,                                d)) - 1) / 9);        int GP2_Sum = 9 * ((int)((Math.Pow(9,                                d)) - 1) / 8);             return GP1_Sum - GP2_Sum;    }         // Driver Code    public static void Main()    {        int d = 1;        Console.WriteLine(findCountUpto(d));                 d = 2;        Console.WriteLine(findCountUpto(d));                 d = 4;        Console.WriteLine(findCountUpto(d));             }} // This code is contributed by Sam007

## PHP

 

Output :

0
9
2619 

Time Complexity : O(1)
Auxiliary Space : O(1)
In the next set we’d see another problem of increased difficulty that can be solved using very similar technique.

This article is contributed by Ashutosh Kumar. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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