diff --git a/README.md b/README.md
index 2404133..d87ec6c 100644
--- a/README.md
+++ b/README.md
@@ -80,6 +80,8 @@ Review the [Contributing Guidelines](https://github.com/donnemartin/interactive-
 
 ## Index
 
+### Challenges Categories
+
 * [Arrays and Strings](#arrays-and-strings)
 * [Linked Lists](#linked-lists)
 * [Stacks and Queues](#stacks-and-queues)
@@ -90,86 +92,201 @@ Review the [Contributing Guidelines](https://github.com/donnemartin/interactive-
 * [Scalability and Memory Limits](#scalability-and-memory-limits)
 * [Concurrency](#concurrency)
 * [Online Judges](#online-judges)
+
+### Installing and Running Challenges
+
+* [Repo Structure](#repo-structure)
+* [Running Challenges](#running-challenges)
 * [Notebook Installation](#notebook-installation)
+* [Nose Installation](#nose-installation)
+
+### Misc
+
 * [Credits](#credits)
-* [Contributing](#contributing)
 * [Contact Info](#contact-info)
 * [License](#license)
 
-## Arrays and Strings
+## Challenges
 
-| Notebook | Problem Statement |
+[Image Credits](#credits)
+
+<br/>
+<p>
+  <img src="https://raw.githubusercontent.com/donnemartin/interactive-coding-challenges/master/images/arrays_nltk.png">
+</p>
+<br/>
+
+### Arrays and Strings
+
+| Challenge | Static Notebook |
 |--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
-| [unique_chars](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/unique_chars/unique_chars_solution.ipynb) | Determine if a string contains unique characters |
-| [reverse_string](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_solution.ipynb) | Reverse characters in a string |
-| [permutation](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/permutation/permutation_solution.ipynb) | Determine if a string is a permutation of another |
-| [compress](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/compress/compress_solution.ipynb) | Compress a string |
-| [rotation](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/rotation/rotation_solution.ipynb) | Determine if a string is a rotation of another |
-| [hash-map](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/hash_map/hash_map_solution.ipynb) | Implement a hash table with set, get, and remove methods |
+| Determine if a string contains unique characters | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/unique_chars/unique_chars_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/unique_chars/unique_chars_solution.ipynb) |
+| Determine if a string is a permutation of another | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/permutation/permutation_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/permutation/permutation_solution.ipynb) |
+| Determine if a string is a rotation of another | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/rotation/rotation_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/rotation/rotation_solution.ipynb) |
+| Compress a string | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/compress/compress_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/compress/compress_solution.ipynb) |
+| Reverse characters in a string | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_solution.ipynb) |
+| Implement a hash table | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/hash_map/hash_map_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/hash_map/hash_map_solution.ipynb) |
+| Find the first non-repeated character in a string | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Remove specified characters in a string | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Reverse words in a string | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Convert a string to an integer | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Convert an integer to a string | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
 
-## Linked Lists
+<br/>
+<p>
+  <img src="https://raw.githubusercontent.com/donnemartin/interactive-coding-challenges/master/images/linked_lists_wikipedia.png">
+</p>
+<br/>
 
-| Notebook | Problem Statement |
+### Linked Lists
+
+| Challenge | Static Notebook |
 |--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
-| [remove_duplicates](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/remove_duplicates/remove_duplicates_solution.ipynb) | Remove duplicates from a linked list |
-| [kth_to_last_elem](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/kth_to_last_elem/kth_to_last_elem_solution.ipynb) | Find the kth to last element of a linked list |
-| [delete_mid](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/delete_mid/delete_mid_solution.ipynb) | Delete a node in the middle of a linked list, given access to only that node |
-| [partition](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/partition/partition_solution.ipynb) | Partition a linked list around a given value |
-| [add_reverse](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/add_reverse/add_reverse_solution.ipynb) | Add two numbers whose digits are stored in a linked list in reverse order |
-| [find_loop_start](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/find_loop_start/find_loop_start_solution.ipynb) | Find the start of a linked list loop |
-| [palindrome](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/palindrome/palindrome_solution.ipynb) | Determine if a linked list is a palindrome |
-| [linked_list](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/linked_list/linked_list_solution.ipynb) | Implement a linked list with insert, find, delete, and print methods |
+| Remove duplicates from a linked list | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/remove_duplicates/remove_duplicates_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/remove_duplicates/remove_duplicates_solution.ipynb) |
+| Find the kth to last element of a linked list | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/kth_to_last_elem/kth_to_last_elem_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/kth_to_last_elem/kth_to_last_elem_solution.ipynb) |
+| Delete a node in the middle of a linked list | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/delete_mid/delete_mid_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/delete_mid/delete_mid_solution.ipynb) |
+| Partition a linked list around a given value | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/partition/partition_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/partition/partition_solution.ipynb) |
+| Add two numbers whose digits are stored in a linked list | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/add_reverse/add_reverse_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/add_reverse/add_reverse_solution.ipynb) |
+| Find the start of a linked list loop | [Challenge]()│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/find_loop_start/find_loop_start_solution.ipynb) |
+| Determine if a linked list is a palindrome | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/palindrome/palindrome_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/palindrome/palindrome_solution.ipynb) |
+| Implement a linked list | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/linked_list/linked_list_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/linked_list/linked_list_solution.ipynb) |
+| Determine if a list is cyclic or acyclic | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
 
-## Stacks and Queues
+<br/>
+<p>
+  <img src="https://raw.githubusercontent.com/donnemartin/interactive-coding-challenges/master/images/stack_queue_wikipedia.png">
+</p>
+<br/>
 
-| Notebook | Problem Statement |
+### Stacks and Queues
+
+| Challenge | Static Notebook |
 |--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
-| [n_stacks](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/n_stacks/n_stacks_solution.ipynb) | Implement n stacks using a single array |
-| [stack_min](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/stack_min/stack_min_solution.ipynb) | Implement a stack that keeps track of its minimum element |
-| [set_of_stacks](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/set_of_stacks/set_of_stacks_solution.ipynb) | Implement a set of stacks class that wraps a list of stacks, each bound by a capacity |
-| [hanoi](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/hanoi/hanoi_solution.ipynb) | Implement the Towers of Hanoi with 3 towers and N disks |
-| [queue_from_stacks](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/queue_from_stacks/queue_from_stacks_solution.ipynb) | Implement a queue using two stacks |
-| [sort_stack](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/sort_stack/sort_stack_solution.ipynb) | Sort a stack using another stack as a buffer |
-| [stack](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/stack/stack_solution.ipynb) | Implement a stack with push, pop, and peek methods using a linked list |
-| [queue](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/queue_list/queue_list_solution.ipynb) | Implement a queue with enqueue and dequeue methods using a linked list |
+| Implement n stacks using a single array | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/n_stacks/n_stacks_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/n_stacks/n_stacks_solution.ipynb) |
+| Implement a stack that keeps track of its minimum element | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/stack_min/stack_min_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/stack_min/stack_min_solution.ipynb) |
+| Implement a set of stacks class that wraps a list of capacity-bounded stacks | [Challenge]()│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/set_of_stacks/set_of_stacks_solution.ipynb) |
+| Implement the Towers of Hanoi with 3 towers and N disks | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/hanoi/hanoi_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/hanoi/hanoi_solution.ipynb) |
+| Implement a queue using two stacks | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/queue_from_stacks/queue_from_stacks_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/queue_from_stacks/queue_from_stacks_solution.ipynb) |
+| Sort a stack using another stack as a buffer | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/sort_stack/sort_stack_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/sort_stack/sort_stack_solution.ipynb) |
+| Implement a stack | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/stack/stack_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/stack/stack_solution.ipynb) |
+| Implement a queue | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/queue_list/queue_list_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/queue_list/queue_list_solution.ipynb) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
 
-## Sorting and Searching
+<br/>
+<p>
+  <img src="https://upload.wikimedia.org/wikipedia/commons/6/6a/Sorting_quicksort_anim.gif">
+</p>
+<br/>
 
-| Notebook | Problem Statement |
+### Sorting and Searching
+
+| Challenge | Static Notebooks |
 |--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
-| [selection_sort](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/selection_sort/selection_sort_solution.ipynb#) | Implement selection sort |
-| [insertion_sort](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/insertion_sort/insertion_sort_solution.ipynb#) | Implement insertion sort |
-| [quick_sort](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/quick_sort/quick_sort_solution.ipynb#) | Implement quick sort |
-| [merge_sort](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/merge_sort/merge_sort_solution.ipynb#) | Implement merge sort |
+| Implement selection sort | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/selection_sort/selection_sort_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/selection_sort/selection_sort_solution.ipynb) |
+| Implement insertion sort | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/insertion_sort/insertion_sort_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/insertion_sort/insertion_sort_solution.ipynb) |
+| Implement quick sort | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/quick_sort/quick_sort_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/quick_sort/quick_sort_solution.ipynb) |
+| Implement merge sort | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/merge_sort/merge_sort_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/sorting_searching/merge_sort/merge_sort_solution.ipynb) |
+| Implement a stable selection sort | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Make an unstable sort stable | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Implement an efficient, in-place version of quicksort | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Given two sorted arrays, merge one into the other in sorted order | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Sort an array of strings so all anagrams are next to each other | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Find an element in a rotated and sorted array of integers | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
 
-## Recursion and Dynamic Programming
+<br/>
+<p>
+  <img src="https://raw.githubusercontent.com/donnemartin/interactive-coding-challenges/master/images/fibonacci_wikipedia.png">
+</p>
+<br/>
 
-| Notebook | Problem Statement |
+### Recursion and Dynamic Programming
+
+| Challenge | Static Notebooks |
 |--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
-| [fibonacci](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/recursion_dynamic/fibonacci/fibonacci_solution.ipynb#) | Implement fibonacci recursively, dynamically, and iteratively |
+| Implement fibonacci recursively, dynamically, and iteratively | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/recursion_dynamic/fibonacci/fibonacci_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/recursion_dynamic/fibonacci/fibonacci_solution.ipynb) |
+| Implement factorial recursively, dynamically, and iteratively | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Perform a binary search on a sorted array of integers | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Print all subsets of a set | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Print all permutations of a string | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Print all combinations of a string | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Print all valid combinations of n-pairs of parentheses | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Implement a paint fill function | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Find all permutations to represent n cents, given 1, 5, 10, 25 cent coins | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
 
-## Trees and Graphs
+<br/>
+<p>
+  <img src="https://raw.githubusercontent.com/donnemartin/interactive-coding-challenges/master/images/binary_tree_wikipedia.png">
+</p>
+<br/>
 
-[Coming Soon]
+### Trees and Graphs
 
-## Bit Manipulation
-
-[Coming Soon]
-
-## Scalability and Memory Limits
-
-[Coming Soon]
-
-## Concurrency
-
-[Coming Soon]
-
-## Online Judges
-
-| Notebook | Problem Statement |
+| Challenge | Static Notebooks |
 |--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
-| [utopian_tree](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/online_judges/utopian_tree/utopian_tree_solution.ipynb) | [View problem statement on HackerRank](https://www.hackerrank.com/challenges/utopian-tree) |
-| [maximizing_xor](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/online_judges/maximizing_xor/maximizing_xor_solution.ipynb) | [View problem statement on HackerRank](https://www.hackerrank.com/challenges/maximizing-xor) |
+| Implement breadth-first search | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Implement depth-first search | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Print a tree using pre-order traversal | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Print a tree using pre-order traversal without recursion | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Print a tree using in-order traversal | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Print a tree using post-order traversal | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Determine the height of a tree | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Determine the lowest common ancestor of two nodes | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Transform a binary tree into a heap | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Implement a right and left rotation on a tree | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Check if a binary tree is balanced | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Check if a binary tree is binary search tree | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+
+<br/>
+<p>
+  <img src="https://raw.githubusercontent.com/donnemartin/interactive-coding-challenges/master/images/probability_distribution_wikipedia.png">
+</p>
+<br/>
+
+### Mathematics and Probability
+
+| Challenge | Static Notebooks |
+|--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
+| Check if a number is prime | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Generate a list of primes | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Determine if two lines on a Cartesian plane intersect | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Using only add, implement multiply, subtract, and divide for ints | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Find the kth number such that the only prime factors are 3, 5, and 7 | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+
+<br/>
+<p>
+  <img src="https://raw.githubusercontent.com/donnemartin/interactive-coding-challenges/master/images/bit_manipulation_wikipedia.png">
+</p>
+<br/>
+
+### Bit Manipulation
+
+| Challenge | Static Notebooks |
+|--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
+| Given a number between 0 and 1, print the binary representation | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Determine the number of bits required to convert integer A to integer B | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Swap odd and even bits in an integer with as few instructions as possible | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Determine the number of 1 bits in the binary representation of a given integer | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
+
+<br/>
+<p>
+  <img src="https://raw.githubusercontent.com/donnemartin/interactive-coding-challenges/master/images/logo_topcoder.png">
+</p>
+<br/>
+
+### Online Judges
+
+| Challenge | Static Notebooks |
+|--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
+| Utopian tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/online_judges/utopian_tree/utopian_tree_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/online_judges/utopian_tree/utopian_tree_solution.ipynb) |
+| Maximizing xor | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/online_judges/maximizing_xor/maximizing_xor_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/online_judges/maximizing_xor/maximizing_xor_solution.ipynb) |
+| Add a challenge | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
 
 ## Notebook Installation