1582 articles
LeetCode 547 Number of Provinces is the canonical connected-components question. Learn the DFS, BFS, and Union Find solutions, master the adjacency-matrix walk, and rehearse the FAANG interview script.
Classic graph reachability problem disguised as a puzzle. Treat each room as a node and each key as a directed edge, then run BFS or DFS from room 0 to check if every room can be visited.
A reachability check between two vertices in an undirected graph. Three optimal approaches: BFS, DFS, and Union Find — each with different trade-offs for follow-up questions about dynamic edges.
BFS from the entrance to find the nearest border empty cell that is not the entrance. Classic BFS shortest-path on a grid with a carefully defined exit condition.
Minimum dice rolls to reach square n² from square 1. The hard part is converting square numbers to board coordinates in Boustrophedon (snake) order. BFS on the state space of squares gives the optimal answer.