Largest K digit number divisible by X

Integers X and K are given. The task is to find the highest K-digit number divisible by X.

Examples:

Input : X = 30, K = 3
Output : 990
990 is the largest three digit 
number divisible by 30.

Input : X = 7, K = 2
Output : 98

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

A simple solution is to try all numbers starting from the largest K digit number (which is 999…K-times) and return the first number divisible by X.

An efficient solution is to use below formula.

ans = MAX - (MAX % X)
where MAX is the largest K digit 
number which is  999...K-times

The formula works on simple school method division. We remove remainder to get the largest divisible number.

C++

// CPP code to find highest K-digit number divisible by X 
#include <bits/stdc++.h> 
using namespace std; 
  
// Function to compute the result 
int answer(int X, int K) 
{ 
    // Computing MAX 
    int MAX = pow(10, K) - 1; 
  
    // returning ans 
    return (MAX - (MAX % X)); 
} 
  
// Driver 
int main() 
{ 
    // Number whose divisible is to be found 
    int X = 30; 
  
    // Max K-digit divisible is to be found 
    int K = 3; 
  
    cout << answer(X, K); 
} 

Java

// Java code to find highest 
// K-digit number divisible by X 
  
import java.io.*; 
import java.lang.*; 
  
class GFG { 
    public static double answer(double X, double K) 
    { 
        double i = 10; 
        // Computing MAX 
        double MAX = Math.pow(i, K) - 1; 
  
        // returning ans 
        return (MAX - (MAX % X)); 
    } 
  
    public static void main(String[] args) 
    { 
  
        // Number whose divisible is to be found 
        double X = 30; 
  
        // Max K-digit divisible is to be found 
        double K = 3; 
  
        System.out.println((int)answer(X, K)); 
    } 
} 
  
// Code contributed by Mohit Gupta_OMG <(0_o)> 

Python3

# Python code to find highest  
# K-digit number divisible by X 
  
def answer(X, K): 
      
    # Computing MAX 
    MAX = pow(10, K) - 1
      
    # returning ans 
    return (MAX - (MAX % X)) 
  
X = 30;  
K = 3;  
  
print(answer(X, K));  
  
# Code contributed by Mohit Gupta_OMG <(0_o)> 

C#

// C# code to find highest 
// K-digit number divisible by X 
  
using System; 
  
class GFG { 
      
    public static double answer(double X, double K) 
    { 
          
        double i = 10; 
          
        // Computing MAX 
        double MAX = Math.Pow(i, K) - 1; 
  
        // returning ans 
        return (MAX - (MAX % X)); 
    } 
  
    public static void Main() 
    { 
  
        // Number whose divisible is to be found 
        double X = 30; 
  
        // Max K-digit divisible is to be found 
        double K = 3; 
  
        Console.WriteLine((int)answer(X, K)); 
    } 
} 
  
// This code is contributed by vt_m. 

PHP

<?php 
// PHP code to find highest K-digit 
// number divisible by X 
  
// Function to compute the result 
function answer($X, $K) 
{ 
      
    // Computing MAX 
    $MAX = pow(10, $K) - 1; 
  
    // returning ans 
    return ($MAX - ($MAX % $X)); 
} 
  
// Driver 
    // Number whose divisible 
    // is to be found 
    $X = 30; 
  
    // Max K-digit divisible 
    // is to be found 
    $K = 3; 
  
    echo answer($X, $K); 
  
// This code is contributed by ajit 
?> 

Output:

This article is contributed by Rohit Thapliyal. 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.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

My Personal Notes

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

C++

Java

Python3

C#

PHP

Recommended Posts: