/** Simple program to illustrate the use of arrays.  Here we ask the user
 *  to enter 10 values, and we find the average, standard deviation,
 *  max and min values.
 *  
 *  Note that it is possible to write this program more efficiently,
 *  and we will explore better techniques later in the course.
 *  This program is just an example showing how to use loops and arrays.
 */
import java.util.Scanner;

public class Array
{
  public static void main(String [] args)
  {
    Scanner kbd = new Scanner(System.in);

    // declare an array "a" of 10 real numbers
    double [] a = new double[10];

    // initialize by asking for input
    int i = 0;
    while (i < 10)
    {
      System.out.print("enter score #" + (i+1) + " --> ");
      a[i] = kbd.nextDouble();
      i = i + 1;
    }

    ////////////////////////////////////////////////////////////////////
    // First we need to find the average before the standard deviation.
    double sum = 0.0;

    i = 0;
    while (i < 10)
    {
      sum += a[i];
      i = i + 1;
    }
    double average = sum / 10;

    ////////////////////////////////////////////////////////////////////
    // The formula to find the standard deviation is as follows:
    // For each score, find its deviation (difference) from the average,
    //   square it, add these squared values, divide by the number of
    //   values, then take the square root.
    sum = 0.0;

    i = 0;
    while (i < 10)
    {
      double diff = a[i] - average;
      sum += diff * diff;
      i = i + 1;
    }
    double standardDeviation = Math.sqrt(sum / 10);

    ////////////////////////////////////////////////////////////////////
    // Now find the extremes of the array.
    // To save time, I'll use the same loop to find both the max & min,
    //   rather than write one loop for each.
    // We assume that the first number in the array is the max (or min),
    //   and then continue the search starting with the 2nd element.
    double max = a[0];
    double min = a[0];

    i = 1;
    while (i < 10)
    {
      if (a[i] > max)
        max = a[i];

      if (a[i] < min)
        min = a[i];

      i = i + 1;
    }

    ////////////////////////////////////////////////////////////////////
    // output
    System.out.printf("\nAverage = %.2f\n", average);
    System.out.printf("Standard deviation = %.2f\n", standardDeviation);
    System.out.printf("Max value = %.2f\n", max);
    System.out.printf("Min value = %.2f\n", min);
  }
}