Project Euler | Problem 16 | Power digit sum

Problem Description:

2^15= 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.

What is the sum of the digits of the number 2^1000 ?

Figure1

Concept:

As result of 2^1000 is very big and we can't store it in any primitive data type so to solve this problem we need to use methods of BigInteger class present in java.math.* package.

Java Program:

	package com.javamultiplex.projecteuler;
	import java.math.BigInteger;
	/**
	*
	* @author Rohit Agarwal
	* @category Project Euler Problems
	* @Problem 16 - Power Digit Sum.
	*
	*/
	public class Problem16 {
	public static void main(String[] args) {
	int a = 2;
	int b = 1000;
	// Converting Integer to BigInteger.
	BigInteger number = new BigInteger(String.valueOf(a));
	// Getting 2^1000.
	BigInteger power = number.pow(b);
	// Converting BigInteger to String.
	String powerInString = String.valueOf(power);
	int length = powerInString.length();
	int sum = 0;
	int temp = 0;
	for (int i = 0; i < length; i++) {
	// Converting char to int.
	temp = powerInString.charAt(i) - 48;
	sum += temp;
	}
	System.out.println("The sum of the digits of the number 2^1000 is : " + sum);
	}
	}

view raw Problem16.java hosted with ❤ by GitHub

Output:

Figure2

Similar Problems:

How to calculate factorial of large number?

How to find first 10 digits of large sum?

References:

https://projecteuler.net/problem=16
https://docs.oracle.com/javase/7/docs/api/java/math/BigInteger.html

Thank you friends, I hope you have clearly understood the solution of this problem. If you have any doubt, suggestion or query please feel free to comment below. You can also discuss this solution in our forum.

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