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import java.util.Scanner;

/**
 * Created by Sahil Pattni on 31-Jan-17.
 */
public class MathTools
{
    public static double absoluteValue(double n)
    {
        if (n < 0)
            return n * -1;
        else
            return n;
    }

    public static double power(double base, int exponent)
    {
        double answer = base;
        if (exponent == 0)
            answer = 1;

        else if (exponent < 0)
        {
            for (int i = 1; i < exponent * -1; i++)
                answer *= base;
            answer = 1/answer;
        }

        else
        {
            for (int i = 1; i < exponent; i++)
                answer *= base;
        }

        return answer;
    }

    public static double nthRoot(double value, int root)
    {
        double answer = -1;
        double initialGuess;
        double nextGuess;
        double difference = 100;
        double tolerance = 0.000000001;

        if (value == 0 || root == 0)
            answer = 0;
        else
        {
            if (root > 0)
                initialGuess = value;
            else
                initialGuess = 1.0/value;

            nextGuess =((1.0/(double) root)*((double)root - 1.0))*(initialGuess)+(value/(power(initialGuess,(root-1))));

            while (difference > tolerance)
            {

                nextGuess = (1.0 / root) * ((root - 1) * (initialGuess) + (value / power(initialGuess, root - 1)));
                difference = absoluteValue(nextGuess - initialGuess);
                initialGuess = nextGuess;
            }

            answer = nextGuess;
        }
        return answer;
    }

    public static String scientificNotation(double n)
    {
        String number = Double.toString(n);
        String answer = "Oops, something went wrong with the method scientificNotation";
        int movementCounter = 0;

        n = ((int)(n*1000000))/1000000.0;

        if(absoluteValue(n) < 1)
        {
            for (int i = 0; i < number.length(); i++)
            {
                if((number.charAt(i) != '0') && (number.charAt(i) != '.'))
                {
                    movementCounter += -1*(i-1);
                    System.out.println(number);
                    number = number.substring(i,i+1)+"."+number.substring(i+1,number.length());
                    System.out.println(number);
                    answer = ""+number;
                    break;

                }
            }
        }
        else if (n >= 10)
        {
            for (int i = 0; i < number.length(); i++)
            {
                if (number.charAt(i) == '.')
                {
                    movementCounter += i-1;
                    number = number.substring(0, i) + number.substring(i+1, number.length());
                    number = number.substring(0,1) + "." + number.substring(1, number.length());
                    answer = ""+number;
                    break;
                }
            }
        }
        else
        {
            answer = ""+n;
        }

        answer += " x 10^" + movementCounter;
        return answer;
    }

    public static void main(String[] args) {
        MathTools m = new MathTools();
        boolean isDone = false;
        Scanner s = new Scanner(System.in);
        boolean toMenu = false;

        while (!isDone)
        {
            System.out.println("Select a number from the menu choices:");
            System.out.println("1 - Absolute Value");
            System.out.println("2 - Power");
            System.out.println("3 - Nth Root");
            System.out.println("4 - Scientific Notation");

            int userChoice = s.nextInt();

            if(userChoice < 1 || userChoice > 4)
                System.out.println("invalid Input");
            else
            {
                if(userChoice == 1)
                {
                    System.out.println("***Absolute Value***");
                    System.out.println("Enter the value");
                    System.out.println(absoluteValue(s.nextDouble()));
                }
                else if (userChoice == 2)
                {
                    System.out.println("***Power***");
                    System.out.println("Enter the value");
                    double base = s.nextDouble();
                    System.out.println("Enter the exponent");
                    int expoent = s.nextInt();
                    System.out.println(power(base, expoent));
                }
                else if (userChoice == 3)
                {
                    System.out.println("***Nth Root***");
                    System.out.println("Enter the value");
                    double value = s.nextDouble();
                    System.out.println("Enter the root");
                    int root = s.nextInt();
                    System.out.println(nthRoot(value, root));
                }
                else if (userChoice == 4)
                {
                    System.out.println("***Scientific Notation***");
                    System.out.println("Enter in the value");
                    System.out.println(scientificNotation(s.nextDouble()));
                }
            }

            System.out.println("Return to the menu? (yes/no)");
            String answer = s.next();

            if (answer.equalsIgnoreCase("no"))
                isDone = true;
            else if (!answer.equalsIgnoreCase("yes"))
                System.out.println("Invalid Input");
        }

        System.out.println("Exiting MathToolsClient...");
    }
}