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.
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 functionint 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 digitimport 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 functionn = 3print(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 digitusing 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?> |
Javascript
<script>// Javascript 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 * Math.pow(9, n - 1);} // Driver code let n = 3; document.write(totalNumber(n)); // This code is contributed by code_hunt.</script> |
648
Time Complexity: O(log n)
Auxiliary Space: O(1)
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