La Fée Verte @Absinthe@qoto.org
The green faerie
Joined Aug 2019
Today's Freebie. It's marked as easy.
This problem was asked by Amazon.
Run-length encoding is a fast and simple method of encoding strings. The basic idea is to represent repeated successive characters as a single count and character. For example, the string "AAAABBBCCDAA" would be encoded as "4A3B2C1D2A".
Implement run-length encoding and decoding. You can assume the string to be encoded have no digits and consists solely of alphabetic characters. You can assume the string to be decoded is valid.
Here's a Freebie, it is marked as "Easy"
This problem was asked by Facebook.
Given a string of round, curly, and square open and closing brackets, return whether the brackets are balanced (well-formed).
For example, given the string "([])[]({})", you should return true.
Given the string "([)]" or "((()", you should return false.
#toyprogrammingchallenge
Here's a freebie!
This problem was asked by Snapchat.
Given an array of time intervals (start, end) for classroom lectures (possibly overlapping), find the minimum number of rooms required.
For example, given [(30, 75), (0, 50), (60, 150)], you should return 2.
Here is one I have been playing with.
Factorials and Fibonacci numbers are traditionally used as examples of recursive functions.
Let's see them done without recursion with reasonable timing.
I apologize for not coming up with a new one this week, but I will post a few freebies.
I discovered discord, and I spent too much free time helping 8th graders do their home work :) Or so it would appear.
Second Freebie!!! This one is marked as "easy"
This problem was asked by Google.
Given two singly linked lists that intersect at some point, find the intersecting node. The lists are non-cyclical.
For example, given A = 3 -> 7 -> 8 -> 10 and B = 99 -> 1 -> 8 -> 10, return the node with value 8.
In this example, assume nodes with the same value are the exact same node objects.
Do this in O(M + N) time (where M and N are the lengths of the lists) and constant space.
Freebie!! Here you go!
This problem was asked by Facebook.
A builder is looking to build a row of N houses that can be of K different colors. He has a goal of minimizing cost while ensuring that no two neighboring houses are of the same color.
Given an N by K matrix where the nth row and kth column represents the cost to build the nth house with kth color, return the minimum cost which achieves this goal.
Here's a freebie. They labeled it as "Hard"
This problem was asked by Google.
Suppose we represent our file system by a string in the following manner:
The string "dir\n\tsubdir1\n\tsubdir2\n\t\tfile.ext" represents:
dir
subdir1
subdir2
file.ext
The directory dir contains an empty sub-directory subdir1 and a sub-directory subdir2 containing a file file.ext.
The string "dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile2.ext" represents:
dir
subdir1
file1.ext
subsubdir1
subdir2
subsubdir2
file2.ext
The directory dir contains two sub-directories subdir1 and subdir2. subdir1 contains a file file1.ext and an empty second-level sub-directory subsubdir1. subdir2 contains a second-level sub-directory subsubdir2 containing a file file2.ext.
We are interested in finding the longest (number of characters) absolute path to a file within our file system. For example, in the second example above, the longest absolute path is "dir/subdir2/subsubdir2/file2.ext", and its length is 32 (not including the double quotes).
Given a string representing the file system in the above format, return the length of the longest absolute path to a file in the abstracted file system. If there is no file in the system, return 0.
Note:
The name of a file contains at least a period and an extension.
The name of a directory or sub-directory will not contain a period.
Okay, this is a big one (description-wise) but basically the idea is to build a Monte Carlo simulation craps simulator to observe strategic differences between "Pass", "Don't Pass", with and without odds.
Here is a description of the necessary craps rules. Ask whatever questions that I haven't made clear.
https://git.qoto.org/Absinthe/crapssim/blob/master/craps.txt
This one is super free! It is not a programming problem so much as a BASH problem.
Using bash parameter expansion only https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html
Given an arbitrarily long path, such as "/head/shoulders/knees/and/toes/eyes/ears/mouth" stored in a variable $TEMP construct a parameter expansion to render only the last two subdirectory and filename like "eyes/ears/mouth" such that you can simply offer the command "echo ${TEMP<stuff goes in here>}"
And yes I do know how much easier it is to do with grep, sed, python, perl, awk <insert your favorite alternate solution here> can do it better and easier. This is a real world problem, and someone on Reddit pointed me in the right direction.
I think I may have an idea for the problem this week. Who likes "Craps?" I will work on the specifics, and think of some additional what-ifs as well.
Here's another freebie, but I am not really sure how to solve it. Guess I wouldn't be getting that job at Google :)
This problem was asked by Google.
The area of a circle is defined as πr^2. Estimate π to 3 decimal places using a Monte Carlo method.
Hint: The basic equation of a circle is x2 + y2 = r2.
Here's a fun freebie! Only because I just recently saw a problem similar :)
This problem was asked by Facebook.
Given a stream of elements too large to store in memory, pick a random element from the stream with uniform probability.
Here's another freebie:
This problem was asked by Amazon.
Given an integer k and a string s, find the length of the longest substring that contains at most k distinct characters.
For example, given s = "abcba" and k = 2, the longest substring with k distinct characters is "bcb".
Okay, here is another freebie.
This problem was asked by Amazon.
There exists a staircase with N steps, and you can climb up either 1 or 2 steps at a time. Given N, write a function that returns the number of unique ways you can climb the staircase. The order of the steps matters.
For example, if N is 4, then there are 5 unique ways:
1, 1, 1, 1
2, 1, 1
1, 2, 1
1, 1, 2
2, 2
What if, instead of being able to climb 1 or 2 steps at a time, you could climb any number from a set of positive integers X? For example, if X = {1, 3, 5}, you could climb 1, 3, or 5 steps at a time.
Here's a freebie,
This problem was asked by Airbnb.
Given a list of integers, write a function that returns the largest sum of non-adjacent numbers. Numbers can be 0 or negative.
For example, [2, 4, 6, 2, 5] should return 13, since we pick 2, 6, and 5. [5, 1, 1, 5] should return 10, since we pick 5 and 5.
Follow-up: Can you do this in O(N) time and constant space?
Okay, maybe you can help me come up with a problem. I can feel it coming on, so here is where I am going:
A trick for pricing things for negotiation is to hide the price encoded. One of the ways of doing this is using a 10 letter isogram such as "upholstery" to convert 0=u, 1=p, 2=h...9=y. So then you could mark a tag or sticker with Tly for $6.49 (with the capitols for dollars and the lower case for cents) Alternatively, you could have an asking price and hide a lowest taking price TlyLuu Meaning that you could ask 6.49 but settle for 4.00. This way someone else could negotiate with the customers, from the person that set the prices.
So writing a program should be unnecessary, the reason for using the isogram is to make it easy to remember and figure it out simply.
So how hard would a program to do this be? Ideas?
This is not a programming question per-se. It, was however, quite interesting and fun to figure out. I am still looking for a new program for this weekend. Unfortunately, no one seemed too interested in last weekend's one, so I may let it float. But I am still looking for one anyway.
An evil warden holds you prisoner, but offers you a chance to escape. There are 3 doors A, B, and C. Two of the doors lead to freedom and the third door leads to lifetime imprisonment, but you do not which door is what type. You are allowed to point to a door and ask a single yes-no question to the warden. If you point to a door that leads to freedom, the warden does answer your question truthfully. But if you point to the door that leads to imprisonment, the warden answers your question randomly, either saying "yes" or "no" by chance. Can you think of a question and figure out a way to escape for sure?
#toyprogrammingchallenge
Another Freebie...
This problem was asked by Facebook.
Given the mapping a = 1, b = 2, ... z = 26, and an encoded message, count the number of ways it can be decoded.
For example, the message '111' would give 3, since it could be decoded as 'aaa', 'ka', and 'ak'.
You can assume that the messages are decodable. For example, '001' is not allowed.
