Assignment 4 at Library

gistfile1.cpp

#include <iostream>
#include <iomanip>

#include <random>

using namespace std;

//See function bodies for comments on these.
int * createArray(int & size);
void findStats(int * arr, int size, int & min, int & max, double & average);
int * searchElement(int * arr, int size, int * element);

int main()
{
	int option	= 0, //Selected option.
		*arr	= 0, //Int pointer to first element in array
		*res	= 0, //Result of search. Pointer to lone int.
		arrSize	= 0, //size of array.
		min		= 0, //Min value in array.
		max		= 0, //Max value in array.
		target	= 0; //Target element to find.

	double
		average	= 0; //Average value in array.
	//Set all the things to 0.
	
	while(true) //Infinite loop (broken in the case block at option 4).
	{
		cout << "Enter a choice: ";
		cin >> option; //Read in option.

		switch(option)
		{
			case 1:
				if (arr) // If arr is not NULL.
					delete [] arr;	//Delete the arr. Note the [] on the delete. If it is not shown there,
									//the program thinks it is only deleting a single pointer to an int.
				arr = createArray(arrSize); //Create an array, passing arrSize so we can get the size back.

				cout << "Array: ";
				for (int i = 0; i < arrSize; i++) //Loop from to to < arrSize
					cout
						<< setw(4) //Set character width to 4.
						<< arr[i]; //Output arr at i
				cout << endl;
				break;
			case 2:
				if (!arr) //If array is not set, hate on the user.
				{
					cout << "Array is not set.";
					break; //Break out of case.
				}
				findStats(arr, arrSize, min, max, average); //Find stats for array and get them back through the reference varibles.
				cout	<< "Array stats: "						<< endl //Let them know what's coming.
						<< "Min: "		<< setw(10) << min		<< endl //Print min
						<< "Max: "		<< setw(10) << max		<< endl //Print max
						<< "Average: "	<< setw(10) << average	<< endl;//Print average
				break;
			case 3:
				if (!arr) //If array isnot set, hate on the user.
				{
					cout << "Array is not set.";
					break; //Break out of case.
				}
				cout << "Select a number to find: ";
				cin >> target; //Note that this is reading into the dereferenced pointer to the target.
				res = searchElement(arr, arrSize, &target);
				if (res) //If res is not 0
					cout << "Number found: " << *res << endl; //Print dereferenced number.
				else
					cout << "Number not found. :(" << endl; //Let the user know our lament.					
				break;
			case 4:
				cout << "Exiting" << endl;
				if (arr) //If array exists
					delete[] arr; //Delete it. Note the [].
				return 0; //Return - out of main an the program exits.
			default:
				cout << "Unknown option: " << option << endl;
		}
	}
	return 0; //Result to be sent back to the OS once this is complete.
}

int * createArray(int & size) //Create array.
{
	cout << "Enter a size: ";
	cin >> size; //Read in size. Note that this goes into the referenced variable.

	if (size > 0) //Size must be > 0 for a valid array.
	{
		int * res = new int[size]; //Declare res as new array of size "size".
		for (int i = 0; i < size; i++)
		{
			res[i] = 1 + rand() % 100;	//The rand function returns a positive integer within a very large range.
									//Control the range by using the % operator (remainder), so that
									//In case (large % small), the result will be up to a maximum of (small - 1)
		}
		return res; //Return the result.
	}
	else
	{
		cout << "Bad size: " << size; //Let the user know they are naughty and entered an invalid size.
		return 0; //NULL pointer.
	}
}

void findStats(int * arr, int size, int & min, int & max, double & average) //Calculate stats for array.
{
	if (size <= 0) //If size is <= 0.
	{
		cout << "Size must be > 0 to calculate stats." << endl; //Let them know how awful they are.
		return; //Return so that we exit the function.
	}
	average = 0; //Set average to 0.
	//min and max don't need to be reset here because they are set to the first element in the loop.

	for (int i = 0; i < size; i++) //Loop from 0 to < size.
	{
		if ((i == 0) || arr[i] < min) //If i is 0 or if arr at i is < min.
			min = arr[i]; //Set min to arr[i]
		if ((i == 0) || arr[i] > max) //If i is 0 set or if arr at i is > max.
			max = arr[i]; //Set max to arr[i].

		average += arr[i]; //Increment average by arr at i.
	}

	average /= size; //Divide average (really just the sum at this point) by the size to get the actual average.
					 //Note that it will automatically cast up from an int to a double, because the compiler goes with
					 //The highest precision type.
}
int * searchElement(int * arr, int size, int * element) //Find element with *element value.
{
	if (size <= 0) //No good. Size too small.
	{
		cout << "Size must be > 0 to search." << endl; //Let them know they are horrible.
		return 0; //Return 0 (failure) so we exit the function.
	}

	for (int i = 0; i < size; i++) //Loop from 0 to < size
		if (arr[i] == *element)  //If array at i is equal to the dereferenced element.
			return (arr + i); //Equal to: &arr[i]; Returning the pointer to the element at i.

	return 0; //Return 0 (failure).
}