**Part 1:** Given 4 rooms full of amphipods with various energy costs for movement (a=1, b=10, c=100, d=1000) and a hallway, how much energy does it take (at minimum) to sort the amphipods into their own rooms with the following conditions:

read more...

**Part 1:** Given a grid of weights, find the minimum path from top left to top right. Return the total weight along that path.

read more...

**Part 1:** Given a list of edges in a bi-directional graph, count the number of paths from `start`

to `end`

such that nodes named with lowercase letters are visited once, and nodes with uppercase letters can be visited any number of times.

read more...