// The StackApps class that implements two Stack applications
// Your name here

import java.util.Scanner;

public class StackApps
{
    // convert a decimal number into a binary number and save it in a stack
    // Do not create any arrays! Do not use any Java libraries to do the convertion.
    // Doing so will result in points deduction.
    public String decToBin(int numDec)
    {
        CharStack stackBinary = new CharStack(64);  // stack used to store the result binary number
        while (numDec > 0) {
	    if (numDec % 2 == 0)
		stackBinary.push('0');
	    else
		stackBinary.push('1');
	    numDec /= 2;
	}
           return stackBinary.toString();  // return a string representation of the stack
    }

    // compute the sum of the two big intergers and save the result in a stack
    // Do not create any arrays! Do not use any Java libraries to do the calculation.
    // Doing so will result in points deduction.
    public String addBigIntegers(String num1, String num2)
    {

        CharStack stackNum1 = new CharStack(64);    // stack used to store number 1
        CharStack stackNum2 = new CharStack(64);    // stack used to store number 2
        CharStack stackResult = new CharStack(64);  // stack used to store the result of the addition
        CharStack remaining;
	for (int i = 0; i < num1.length(); i += 1)
	    stackNum1.push(num1.charAt(i));
	for (int i = 0; i < num2.length(); i += 1)
	    stackNum2.push(num2.charAt(i));

	int carry = 0;
	int a;
	int b;
	int result;
	while (!(stackNum1.isEmpty() || stackNum2.isEmpty())) {
	    a = (int) (stackNum1.pop() - '0');
	    b = (int) (stackNum2.pop() - '0');
	    result = (a+b+carry);
	    carry = result/10;
	    stackResult.push((char)((result%10) +  '0'));
	}
	if (stackNum1.isEmpty())
	    remaining = stackNum2;
	else
	    remaining = stackNum1;
	while (!(remaining.isEmpty())) {
	    a = (int) (remaining.pop() - '0');
	    result = (a+carry);
	    carry = result/10;
	    stackResult.push((char)((result%10) + '0'));
	}
	if (carry > 0)
	    stackResult.push((char)(carry + '0'));
        return stackResult.toString();  // return a string representation of the stack
    }
}