Graph Valid Tree
Given n nodes and edges array where each [a, b] is an undirected edge Return True if graph is a valid tree (connected, acyclic, n-1 edges) Example: n = 5, edges = [[0,1],[0,2],[0,3],[1,4]] => True Example: n = 5, edges = [[0,1],[1,2],[2,3],[1,3],[1,4]] => False (cycle)
You're checking whether a set of connections forms a proper tree—one connected piece with no loops. It's a favorite in interviews because it forces you to articulate what makes a tree a tree, then verify those properties cleanly. The classic gotcha is accidentally detecting cycles when you revisit your parent node. Once you're comfortable here, connected-component problems become much easier.
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