Question

Problem:

Write a Java program that will convert a number(x) in base r to base 10.

The program should also meet the following requirements:

· Base r is an input and must be validated ; r is from 2 to 9 only

· The number x is an input and must be stored in an int type variable. Do not convert x to

string.

· Use of String type variable is not allowed.

· Use of arrays is not allowed.

· Use of built-in method that converts a given number to another base is not allowed.

· Your program should execute for as long as the user wants to continue

Assume that the user will input a valid number.

Note: This program converts X^r to Y^10

Where :

X^r - a number in base r

r – is from 2 to 9 only

Y^10 – the equivalent number in base 10

Answer 1

class Main
{
    public static void main(String[] args)
    {
        String s1 = "1010"; 
        String s2 = "2314";
        String s3 = "435";


        System.out.println(convert_to_Base(s1,2));
        System.out.println(convert_to_Base(s2,4));
        System.out.println(convert_to_Base(s3,5));
    }


    private static final String SYMBOLS = "0123456789ABCDEF";
    public static long convert_to_Base(String num, int b)
    {
        long res = 0;
        int pos = num.length(); 
        for (char c : num.toCharArray())
        {
            int value = SYMBOLS.indexOf(c);
            res += value * pow(b,--pos); 
        }
        return res;
    }
    private static long pow(int val, int x)
    {
        if (x == 0) return 1;
        return val * pow(val,x-1);
    }
}