/********************************************
 *                 Rollin92                 *
 *          http://www.warpdworld.com       *
 *      The Program accepts two integers    *
 *     and adds them together. It can       *
 *        handle up to 300 digits.          *
 ********************************************/


#include <iostream.h>
#include <string.h>


int main()
{
	//Variable declaration
	char buffer[300];
	int* num1;
	int* num2;
	int* answer;
	int num1_length = 0;
	int num2_length = 0;
	int longest = 0;
	int i = 0;
	int j = 0;
	int k = 0;
	int carry = 0;
	int sum = 0;

	//Prompt user for first number
	cout << "Enter the first integer, up to 300 digits: ";
	cin.getline(buffer,sizeof(buffer));

	//Dynamically allocate space for number
	num1 = new int[strlen(buffer)];
	num1_length = strlen(buffer);

	//Copy number into integer array
	for(i = 0; i < strlen(buffer); i++)
	{
		//I used - 48 to change the number from its ascii value to the actual number
		//Probably could use atoi instead, but this works
		num1[i] = (buffer[i] - 48);
	}

	//Get second number from user
	cout << endl << endl << "Enter the second integer, up to 300 digits: ";
	cin.getline(buffer,sizeof(buffer));

	//Dynamically allocate space for number
	num2 = new int[strlen(buffer)];
	num2_length = strlen(buffer);

	//Copy number into integer array
	for(i = 0; i < strlen(buffer); i++)
	{
		num2[i] = (buffer[i] - 48);
	}

	//if statements used to see which number is longest
	//The answer can't be longer than longest number + 1
	//So I used this to figure out how long to make the answer array
	if((num1_length) > (num2_length))
	{
		answer = new int[num1_length + 1];
		//k doesn't get a plus 1 since arrays start at 0
		k = num1_length;
		longest = num1_length + 1;
	}

	else
	{
		answer = new int[num2_length + 1];
		//k doesn't get a plus 1 since arrays start at 0
		k = num2_length;
		longest = num2_length + 1;
	}

	//Set i and j to the length of numbers 1 and 2
	//Use - 1 since array starts at 0
	i = (num1_length - 1);
	j = (num2_length - 1);

	//While loop for the addition of the numbers
	//Add them one at a time
	while((i >= 0) && (j >= 0))
	{
		//Add the numbers and any carry together and
		//hold in sum
		sum = num1[i] + num2[j] + carry;

		//If no carry
		if(sum < 10)
		{
			answer[k] = sum;
			carry = 0;
		}

		//If there is a carry
		else
		{
			answer[k] = (sum - 10);
			carry = 1;
		}

		//Decrement variables
		i--;
		j--;
		k--;
	}

	//This runs if number2 is longer than number 1
	//It dumps the rest of number2 into the answer
	//array. It does take care of the carry bit also
	if((i <= 0) && (j >= 0))
	{
		while(j >= 0)
		{
			sum = num2[j] + carry;

			if(sum < 10)
			{
				answer[k] = sum;
				carry = 0;
			}

			else
			{
				answer[k] = (sum - 10);
				carry = 1;
			}

			j--;
			k--;
		}
	}

	//This runs if number1 is longer than number 2
	//It dumps the rest of number1 into the answer
	//array. It handles the carry bit if there is one.
	if((i >= 0) && (j <= 0))
	{
		while(i >= 0)
		{
			sum = num1[i] + carry;

			if(sum < 10)
			{
				answer[k] = sum;
				carry = 0;
			}

			else
			{
				answer[k] = (sum - 10);
				carry = 1;
			}

			i--;
			k--;
		}
	}

	//Part of display
	cout << endl << endl << "Answer:";

	//This runs if there is a carry bit left over
	//but both numbers have already been added
	//It puts the carry into the front of the 
	//answer array.
	if((i <= 0) && (j <= 0) && (carry == 1))
	{
		answer[k] = carry;
		
		//Displays the answer
		for(i = 0; i < longest; i++)
		{
			cout << answer[i];
		}
	}

	//If there isn't a carry then this runs
	else
	{
		//Displays the answer
		//It skips the first element of the
		//answer array since that element is
		//reserved for the carry that could be
		//left over at the end of the addition
		for(i = 1; i < longest; i++)
		{
			cout << answer[i];
		}
	}

	cout << endl << endl;

	return 0;
}//End of main

/*
Sample Run:

Enter the first integer, up to 300 digits: 999999999999999999999999999999


Enter the second integer, up to 300 digits: 999999999999999999999999999999


Answer:1999999999999999999999999999998

Press any key to continue

*/