/* This program will input a list of numbers from the user to store in an array and then use methods to perform various
 * computations on the array's values such as finding the minimum, the maximum, the difference between max and min, the sum, the
 * average, the standard deviation and the index of the first occurrence of the minimum and the last occurrence of
 * the maximum.  This program is primarily set up to demonstrate both arrays and methods where some methods will be
 * called from multiple places in the code. */
 
import java.util.Scanner;

public class ArrayMadness
{
	public static void main(String[] args)
	{
		Scanner in = new Scanner(System.in);
		int[] values = new int[100];
		int number = getValues(in, values);					// this method will input the array and return the size of the array
		int max = findMax(values, number);					// obtain the maximum value
		int min = findMin(values, number);					// obtain the minimum value
		System.out.println();
		System.out.println("The maximum value is " + max);
		System.out.println("The minimum value is " + min);
				// note we could just compute max - min but I wanted to show modularity by having findDiff call the findMax and findMin methods
		System.out.println("The difference between max and min is " + findDiff(values, number));
		System.out.println("The sum of the values is " + findSum(values, number));		
		System.out.println("The average value is " + findAvg(values, number));
		System.out.println("The standard deviation is " + findSTD(values, number));
		System.out.println("The first instance of " + min + " is " + findFirst(values, number, min));
		System.out.println("The last instance of " + max + " is " + findLast(values, number, max));
	}
	
	
	// This method receives a Scanner and an empty array that can hold up to 100 elements and inputs elements from the user
	// The method uses a sentinnel loop iterating while the input >= 0 or until the array is filled
	// The array is automatically returned via the parameter list because it is an object, the method returns the number of
	//    elements input so that main can know how many elements are in the array to control later for loops
	public static int getValues(Scanner in, int[] array)
	{
		int number = 0;
		int temp;
		System.out.print("Enter positive values, negative to quit, no more than 100 total values:  ");
		temp = in.nextInt();
		while(temp>=0&&number<100)
		{
			array[number]=temp;
			number++;
			System.out.print("Enter the next positive value, negative to quit, no more than 100 total values:  ");
			temp = in.nextInt();
		}
		return number;
	}
	
	// if there are values in the array, find and return the maximum otherwise return an "error code" value of -1
	public static int findMax(int[] values, int number)
	{
		if(number>0)
		{
			int max=values[0];								// assume values[0] is the largest
			for(int i=1;i<number;i++)						// search the rest of the array and for any
				if(values[i]>max) max=values[i];			//    value > max, remember it as the new max
			return max;
		}
		else return -1;
	}
	
	// if there are values in the array, find and return the minimum otherwise return an "error code" value of -1
	public static int findMin(int[] values, int number)
	{
		if(number>0)
		{
			int min=values[0];							// assume values[0] is the minimum	
			for(int i=1;i<number;i++)					// search the rest of the array comparing each new element to min and
				if(values[i]<min) min=values[i];			// if an element < min, remember it as the new min
			return min;
		}
		else return -1;
	}
	
	// for modularity sake, call findMin and findMax and compute and return their difference
	public static int findDiff(int[] values, int number)
	{
		int min = findMin(values, number);
		int max = findMax(values, number);
		return max - min;
	}
	
	// if the array has elements, iterate through the array summing up the values and returning the sum, otherwise return -1
	public static int findSum(int[] values, int number)
	{
		int sum = 0;
		if(number>0)
		{
			for(int i=0;i<number;i++)
				sum+=values[i];
			return sum;
		}
		else return -1;
	}
	
	// if the array has elements, call findSum to obtain the sum and use it to return the average, otherwise return -1
	public static double findAvg(int[] values, int number)
	{
		int sum = findSum(values, number);
		if(number>0)
			return (double)sum/number;
		else return -1.0;
	}
	
	// if the array has elements, call findAvg to obtain the average and use it to compute and return the standard deviation
	// otherwise return -1
	// STD:  sum of each (values[i] - average)^2, take result, divide by N and take the sqrt
	public static double findSTD(int[] values, int number)
	{
		double avg = findAvg(values, number);
		double sum = 0.0;
		if(avg!=-1.0)
		{
			for(int i=0;i<number;i++)
				sum = sum + Math.pow(values[i]-avg,2);
			return Math.sqrt(sum/number);
		}
		else return -1.0;
	}
	
	// starting from the beginning of the array, search for target and return the location (index) of where it was found, -1 if not found
	public static int findFirst(int[] values, int number, int target)
	{
		for(int i=0;i<number;i++)
			if(values[i]==target) return i;
		return -1;
	}
	
	// starting from the end of the array, search for target and return the location (index) of where it was found, -1 if not found	
	public static int findLast(int[] values, int number, int target)
	{
		for(int i=number-1;i>=0;i--)
			if(values[i]==target) return i;
		return -1;
	}
}