Problem Link: https://cses.fi/problemset/task/1194
The idea was actually pretty straightforward, just an implementation of multisource BFS (160+ lines).
My submission is still TLE on one test case (19th test case), and the rest were AC. Still can't figure it out.
Here's my submission, perhaps someone out there is willing to give a hand. Language: C++ 17. https://cses.fi/paste/233c9c55d599a6ba247883/