Question

I am trying to solve this “exponentiation” problem.

Here is the code that I have written

import java.util.Scanner;
import java.util.ArrayList;
import java.math.BigInteger;
import java.io.*;
import java.math.*;
import java.util.ArrayList;


public class Main {
    public static void main(String[] args) {
        Scanner Input = new Scanner(System.in);
        BigDecimal R,f;// = new BigInteger();
        ArrayList <String> ans = new ArrayList <String> ();
        int n;
   /////  I dont know how to deal with it         
    while(  R = Input.nextBigDecimal(), n = Input.nextInt() )
    ////
    f = R.pow(n);
    f = f.stripTrailingZeros();
    String s = f.toPlainString();
    String answer = "";
    answer = s;

    if(s.charAt(0) == '0')
        s = s.substring(1);
    ans.add(answer);

    System.out.println(s);


    }

}

Now The question that I want to ask is that how would I take input until the end of file?
(I have solved such problems using c++ using while(cin >> v >> s) etc ) But I don’t know how to solve this.

Answer 1

Scanner class has also hasNextBigDecimal() method, so you would like to do:

while ( Input.hasNextBigDecimal() ) {
    R = Input.nextBigDecimal();
    n = Input.nextInt();
    ... // processing
}

Scanner is slow for huge input files. I’m using BufferedReader if the line has well known format (for example two numbers separated by space):

BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );
String parts[] = br.readLine().split( " " );

If you want to use java, you should learn also Java naming conventions.

And even better than split is to use StringTokenizer, it’s quicker.