Daily coding problem

These are my solutions to https://dailycodingproblem.com, a great resource to practice coding interviews.

I have copied problem definitions and examples verbatim from the one I received, but they might occasionally differ from yours when questions have been updated to improve clarity or provide additional tests. Notes added after examples are comments of mine.

Problems

Each problem comes with a description, a unit tests' battery and a solution.

Just looking for a FizzBuzz implementation? Find a few here!

#	Description	Problem	Solution
01	Interleave the elements of a stack using a queue	problem	solution
02	Product of every other number in an array	problem	solution
03	Serialize a tree into a string and back	problem	solution
04	Find the first missing positive integer	problem	solution
05	Implement Lisp's car and cdr given cons	problem	solution
06	Implement a XOR linked list	problem	solution
07	Count the number of decodings for a message	problem	solution
08	Count the number of unival subtrees	problem	solution
09	Largest sum of non-adjacent numbers	problem	solution
10	Call a function after n milliseconds	problem	solution
11	Implement an autocomplete system	problem	solution
12	Count the ways to climb a staircase	problem	solution
13	Longest substring made of k distinct characters	problem	solution
14	Monte-Carlo estimate of Pi	problem	solution
15	Pick a random element from a stream	problem	solution
16	Implement an purchase orders' log	problem	solution
17	Longest path in a filesystem	problem	solution
18	Max of each sub-array of length k	problem	solution
19	House coloring problem	problem	solution
20	Find intersection between single linked lists	problem	solution
21	Number of classrooms required given schedule	problem	solution
22	Split a string of words into parts	problem	solution
23	Solve a maze	problem	solution
24	Implement locking in a binary tree	problem	solution
25	Implement regular expression matcher	problem	solution
26	Remove the kth element from a linked list	problem	solution
27	Is a string of brackets well-formed?	problem	solution
28	Write an algorithm to justify text	problem	solution
29	Run-length encoding and decoding	problem	solution
30	Water trapped in an elevation map	problem	solution
31	Compute the edit distance between two strings	problem	solution
32	Possibility of arbitration in currency exchange	problem	solution
33	Compute the running median of a sequence of numbers	problem	solution
34	Fewest characters to make a palindrome	problem	solution
35	Segregate the values of an array	problem	solution
36	Find the second largest node in the tree	problem	solution
37	Generate the power set of a set	problem	solution
38	Solve the N-queens problem	problem	solution
39	Implement Conway's Game of Life	problem	solution
40	Find the non-duplicated integer	problem	solution
41	Itinerary from flights' list	problem	solution
42	Subset of an array that adds up to k	problem	solution
43	Implement a stack with a max() operation	problem	solution
44	Determine how "out of order" an array A is	problem	solution
45	Implement rand5() given rand7()	problem	solution
46	Find the longest contiguous palindrome	problem	solution
47	Max profit from a stock time-series	problem	solution
48	Reconstruct tree from pre-order and in-order traversals	problem	solution
49	Find the maximum sum of any contiguous subarray	problem	solution
50	Compute an arithmetic expression tree	problem	solution

How to contribute

Pull requests warmly welcomed if you spot issues with any of my solutions!

You can also contribute additional unit tests for interesting untested scenarios.

Running tests

To run all the unit tests for the provided solutions, use the run_tests.py scripts inside the problems and legacy directories.

Python 2.7 compatible versions

Python 2.7 compatible versions are available under the legacy directory.