Partitioning a Linked List

2021-04-20

One more fairly standard tech interview problem (for better or for worse, you’re likely to see one of these if you go for a programming job):

Given a linked list and an element x. Partition the list so that all elements less than x are before elements greater than or equal to x, but do not otherwise change the order of the elements.

Dynamic Programming over a Matrix

2021-04-13

Another LeetCode problem. Given an MxN matrix of numbers, find the longest path of strictly increasing numbers. So for example in this matrix: 994 668 211 You can start with the 1 in the bottom center, go left to the two, then up to the 6, and 9. That’s the longest path, so return a 4. In this 3x3 case, it’s really easy to just brute force. Calculate all possible paths.

Phone Words--In English!

2021-04-09

Okay, let’s take this one step further. Rather than generating just phone words, let’s actually generate phone words. Someone has provided a list of words in English as a package, so we’ll add a filter to add that to our comprehension: from english_words import english_words_set def letterCombinations(self, digits: str) -> List[str]: if not digits: return [] letters = { '1': '', '2': 'abc', '3': 'def', '4': 'ghi', '5': 'jkl', '6': 'mno', '7': 'pqrs', '8': 'tuv', '9': 'wxyz', '0': ' ', } return [ word for product in itertools.

Phone Words

2021-04-06

Working through a few problems on LeetCode. I haven’t quite decided what I think of the site, but it’s a fun way to play with simple algorithms. Figured I might as well write up any I find interesting.

First interesting problem:

Given a standard lettered keypad, generate all words from a given phone number.