Java Program for Largest K digit number divisible by X

Integers X and K are given. The task is to find 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

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.

// 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 contributes by Mohit Gupta_OMG <(0_o)>

Output:

990

To understand Math.pow() function, please refer point 18 of the article :
https://www.geeksforgeeks.org/java-lang-math-class-java-set-2/

Please refer complete article on Largest K digit number divisible by X for more details!