RecursionPractice

// RecursionPractice.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>

using namespace std;

//The following 2 declarations are used in problems 27, 28, 29
/*1*/const int MAX_CAPACITY = 20;
/*2*/typedef int ElementType;
/*3*/typedef ElementType ArrayType;

int getNumber()
{
	int n = 0;
	cout << "Enter a number: ";
	cin >> n;
	return n;
}


int f(char ch1, char ch2, int &n)
{
	n++;
	if (ch1 > ch2)
		return 0;
	if (ch1 + 1 == ch2)
		return 1;
	//else
	cout << "Characters being returned ch1: " << static_cast<char>(ch1 + 1) << " , ch2: " << static_cast<char>(ch2 - 1) << endl;
	return f(ch1 + 1, ch2 - 1, n) + 2;
}

unsigned problem21(unsigned n)
{
	if (n == 0)
		return 0;
	//else
	return 1 + problem21(n / 10);
}

int problem23(int n)
{
	if (n < 10)
		cout << n;
	else
	{
		cout << (n % 10);
		return problem23(n / 10);
	}
	
}

void reverseArray(ArrayType a[], int first, int last)
//Reverse the contents of a[first], ... , a[last]
{
	if (last == first)
		return;
	else
	{
		cout << a[--last] << " ";
		reverseArray(a, first, last);
	}

}

int sumArray(ArrayType a[], int n)
//Return the sum of a[0], ... , a[n-1]
{
	if (n == 0)
		return 0;
	//else
	return a[n] + sumArray(a, --n);
}

int location(ArrayType a[], int first, int last, ElementType elm)
//Return the location of elm in a[first], ..., a[last]
{
	if (first == last)
		return 0;
	if (elm != a[first])
		location(a, first + 1, last, elm);
	else
		return first + 1;
}

int hailstone(int n)
{
	static int i = 0;
	if (n == 1)
		return i;
	if (n % 2) //If n is odd, remainder != 0
	{
		hailstone(3 * n + 1);
		i++;
	}
	else if (!(n % 2)) //If n is even, remainder is zero
	{
		hailstone(n / 2);
		i++;
	}
		
}

void fillArray(int *p, int maxValue)
{
	if (maxValue == 0)
		return;
	else
	{
		*p = maxValue;
		p--;
		fillArray(p, maxValue - 1);
	}
}

int main()
{
	/*cout << "Exercises 10.1 #7" << endl;
	int num;
	int count = 0;
	num = f('a', 'e', count);
	cout << num << endl;
	cout << "coutn: " << count << endl;

	count = 0;
	num = f('h', 'c', count);
	cout << num << endl;
	cout << "count: " << count << endl;*/

	cout << "PROBLEM 21" << endl;
	int z = 0;
	z = getNumber();
	cout << "Number of digits in nonnegative integer 12345: " << problem21(z) << endl;
	cout << endl;

	cout << "PROBLEM 23" << endl;
	z = getNumber();
	problem23(z);
	cout << endl;

	cout << "PROBLEM 27" << endl;
	cout << "Fill array with 1, 3, 5, 7, 9" << endl;
	ElementType ary[MAX_CAPACITY];
	ElementType *ptr;
	ptr = &ary[MAX_CAPACITY-1];
	fillArray(ptr, MAX_CAPACITY); //Fill array function for problem # 4
	reverseArray(ary, 0, MAX_CAPACITY);
	cout << endl;

	cout << "PROBLEM 28" << endl;
	cout << "Use Problem 27 array" << endl;
	cout << "Sum of array: " << sumArray(ary, MAX_CAPACITY) << endl;
	cout << endl;

	cout << "PROBLEM 29" << endl;
	cout << "Use Problem 27 array" << endl;
	int value = 0, index = 0;
	value = getNumber();
	index = location(ary, 0, MAX_CAPACITY, value);
	if (index)
		cout << "The number " << value << " is located in index " << index << endl;
	else
		cout << "Value not found" << endl;
	cout << endl;

	cout << "2. HAILSTONES ALGORITHM" << endl;
	int iterations = 0;
	iterations = hailstone(getNumber());
	cout << "It takes " << iterations << " iterations of the hailstone algorithm "
		<< "for value to reach 1." << endl;
	cout << endl;

	cout << "3. Print out Linked List program in reverse recursively";
	//Included in separate file
	cout << "Included in separate file" << endl;
	cout << endl;

	cout << "4. Fill array of size 20 with values of 1-20" << endl;
	// 'ElementType *ptr = &ary[MAX_CAPACITY];' declared on line 146
	// fillArray(ptr, MAX_CAPACITY);
	cout << "Function was utilized in problem 1, first used on line 148" << endl;
	cout << endl;


	

	
    return 0;
}