I wrote this program to find if a given input is power of 2 , this program is not running for very large number such as 10^18 or so. what should i do

Question

This is a program to check if an input is power of 2 or not. This program is running fine for inputs up to 8 digits but when I am giving input like 10¹⁸, it is not working, What should I do?

import java.util.Scanner;
    public class search {
        public static void main(String [] args){
            //to take how many inputs are there
            Scanner sc = new Scanner(System.in);
            int k ;
            k = sc.nextInt();
            for(int i = 0 ;i<k;i++){
            // input number n
            long  n ;


            n = sc.nextInt();

            if ((n > 0) && ((n & (n - 1)) == 0)){
                System.out.println("YES");
            }
            else{
                System.out.println("NO");
            }
        }
    }
}

score 7 · Accepted Answer · answered Jan 01 '16 at 07:22

The problem is that 10¹⁸ is out of range of Java int, which stores numbers up to 2³¹-1, or roughly 2*10⁹. You can expand the range of your program by using long in place of int to accept numbers up to 9*10¹⁸, or to make it accept virtually unlimited range by using BigInteger:

BigInteger n = new BigInteger(numericString);
BigInteger test = n.and(n.subtract(BigInteger.ONE));
if (test.equals(BigInteger.ZERO)) {
    ...
}

score 1 · Answer 2 · edited May 23 '17 at 11:59

1

You need to get your input number as String then use BigInteger class to avoid limit surpassing problem,

BigInteger inputNumber = new BigInteger(inputString);

Also, refer What does BigInteger having no limit mean? to know more about BigInteger limits.

edited May 23 '17 at 11:59

Community

1
1

answered Jan 01 '16 at 07:28

Sabir Khan

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score 0 · Answer 3 · answered Jan 01 '16 at 08:48

0

If the long number range is enough, you can just change

n = sc.nextInt();

to

n = sc.nextLong();

At the moment, n is only set to an integer and therefore limited to the int number range.

answered Jan 01 '16 at 08:48

Henry

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score 0 · Answer 4 · answered Jan 01 '16 at 08:56

Better Use Class BigInteger it implement Serializable, Comparable<BigInteger> .BigInteger provides operations for modular arithmetic, GCD calculation, primality testing, prime generation, bit manipulation, and a few other miscellaneous operations.

input="Number"
BigInteger number = new BigInteger(input);
//Do your stuff

Happy to help thanks

score 0 · Answer 5 · answered Jan 03 '16 at 09:55

0

Take the input in long:

 k = sc.nextLong();

answered Jan 03 '16 at 09:55

MrAP

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I wrote this program to find if a given input is power of 2 , this program is not running for very large number such as 10^18 or so. what should i do

5 Answers5