## Problem

As you may already know from Fundamentals or Computer Architecture, integer values in C and C++ are limited by the number of bits used to represent that data. For instance, a 64-bit unsigned integer has the maximum value of `2^64 - 1` or `18446744073709551615`.

To represent integers of arbitrary length, we can use a singly linked list data structure such that that a node in the linked list corresponds to a single digit in the integer.

For instance, the number `123` can be stored as linked-list that looks like the following:

```[ 3 ] -> [ 2 ] -> [ 1 ] -> NULL
```

Note that the first or head node in this list contains the least significant digit (in this case `3`), while the last node contains the most significant digit (`1`).

For this problem, you are to read in pairs of arbitrary length integers into singly linked lists, then use the lists to add the two numbers, and finally output the results.

#### Inspiration

Note, this problem is inspired by Problem 8.19 from Elements of Programming Interviews and Problem 2.5 from Cracking the Code Interview.

## Input

You will be given a series of integers from standard input in the follow format:

```integer1 integer2
integer1 integer2
...
integer1 integer2
```

Each integer is of arbitrary length. Moreover, `integer1` is not guaranteed to be the same length as `integer2`.

## Output

You are to add each pair of integers and then output the resulting total as a single number:

```result1
result2
...
resultN
```

## Example

Given the following input:

```1 1
123 123
1 12
```

Your program should output the following:

```2
246
13
```

## Requirements

Your solution must meet the following requirements:

1. You must create a custom linked list (ie. you cannot use std::list).

3. If you dynamically allocate memory, then you must be sure you manage it properly (ie. no memory leaks or segmentation faults).

## Hints

1. You may wish to read the integers in as std::strings.

2. You may wish to define a `struct Node`.

3. You may wish to define a `struct List` with an operation to add an item to the list.

4. You may wish to define a function that takes two lists and returns a list that contains the sum of the two input lists.

5. Be sure to account for the carry when you perform addition.

## Preparation

Before working on this problem, you should use git to pull the changes from the upstream assignments repository:

```# Go to your repository
\$ cd path/to/repo

# Make sure we are on master branch
\$ git checkout master

\$ git remote add upstream https://gitlab.com/nd-cse-30331-fa16/assignments.git

# Fetch and merge upstream changes into local repository
\$ git pull upstream master
From gitlab.com:nd-cse-30331-fa16/assignments
Merge made by the 'recursive' strategy.
challenge02/Makefile     | 26 ++++++++++++++++++++++++++
challenge02/input        | 11 +++++++++++
challenge02/output       | 11 +++++++++++
challenge02/solution.cpp |  9 +++++++++
4 files changed, 57 insertions(+)
create mode 100644 challenge02/Makefile
create mode 100644 challenge02/input
create mode 100644 challenge02/output
create mode 100644 challenge02/solution.cpp
```

When you perform the `git pull` you may be asked to write a commit message. You can simply use the default message by closing the text editor it brings up.

Once this is complete, you should have the `Makefile`, `input`, `output`, and `solution.cpp` for this challenge.

#### Updated Testing Framework

The testing framework has been updated so that `make test` will only run the test for the particular challenge rather than for all challenges. When you do a `pull`, you should see that `Makefile` and `.gitlab-ci.yml` have been updated.

## Submission

To submit your solution, you must initiate a Merge Request in your private assignments repository and assign it to the appropriate TA from the Challenge 02 - TA assignment list.

#### Development Branch

To facility the Merge Request workflow, you must do your development in its own branch:

```\$ cd path/to/repo                   # Go to your repository
\$ git checkout master               # Make sure we are on master branch
\$ git pull                          # Make sure we have changes for GitLab
\$ git checkout -b challenge02       # Create challenge02 branch