Accounts Merge
Given accounts where accounts[i] = [name, email1, email2, ...] Merge accounts belonging to same person (same email) Return merged accounts: [name, sorted_emails...] Order of accounts doesn't matter
Accounts Merge is a traversal problem: the hard part is modeling the state you visit. Interviewers love it because it reveals your traversal modeling and your edge-case discipline. The trap is revisiting states or missing a base case; your visited/queue logic needs to be tight.
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