Number of n digit numbers that do not contain 9

Given a number n, find how many n digit number can be formed that does not contain 9 as it’s digit.

Examples:

Input : 1
Output : 8
Explanation :
Except 9, all numbers are possible

Input : 2
Output : 72
Explanation :
Except numbers from 90 - 99 and all
two digit numbers that does not end
with 9 are possible.

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Total numbers of n digit number that can be formed will be 9*10^(n-1) as except first position all digits can be filled with 10 numbers (0-9). If a digit 9 is eliminated from the list then total number of n digit number will be 8*9^(n-1).

Below is the implementation of above idea:

C++

// CPP program to find number of n  
// digit numbers that do not  
// contain 9 as it's digit 
#include <bits/stdc++.h> 
using namespace std; 
  
// function to find number of  
// n digit numbers possible  
int totalNumber(int n) 
{ 
    return 8*pow(9, n - 1); 
} 
  
// driver function 
int main() 
{ 
    int n = 3; 
    cout << totalNumber(n); 
    return 0; 
} 

Java

// Java program to find number of   
// n digit numbers that do not  
// contain 9 as it's digit 
import java.io.*; 
  
public class GFG 
{ 
      
// function to find number of  
// n digit numbers possible  
static int totalNumber(int n) 
{ 
    return 8 * (int)Math.pow(9, n - 1); 
} 
  
    // Driver Code 
    static public void main (String[] args) 
    { 
        int n = 3; 
        System.out.println(totalNumber(n)); 
          
    } 
} 
  
// This code is contributed by vt_m. 

Python3

# python program to find number of n  
# digit numbers that do not  
# contain 9 as it's digit 
  
# function to find number of  
# n digit numbers possible  
def totalNumber(n): 
      
    return 8 * pow(9, n - 1); 
   
# driver function 
n = 3
print(totalNumber(n)) 
  
# This code is contributed by Sam007 

C#

// C# program to find number of   
// n digit numbers that do not  
// contain 9 as it's digit 
using System; 
  
public class GFG 
{ 
      
// function to find number of  
// n digit numbers possible  
static int totalNumber(int n) 
{ 
    return 8 * (int)Math.Pow(9, n - 1); 
} 
  
    // Driver Code 
    static public void Main () 
    { 
        int n = 3; 
        Console.WriteLine(totalNumber(n)); 
          
    } 
} 
  
// This code is contributed by vt_m. 

php

<?php 
// php program to find number of n  
// digit numbers that do not  
// contain 9 as it's digit 
  
// function to find number of  
// n digit numbers possible  
function totalNumber($n) 
{ 
    return 8 * pow(9, $n - 1); 
} 
   
// driver function 
$n = 3; 
print(totalNumber($n)) 
  
// This code is contributed by Sam007 
?> 

Output:

This article is contributed by Dibyendu Roy Chaudhuri. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

php

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