LeetCode Card 298 — Union-Find / Structure
Pattern signal
This pattern usually appears when the prompt involves dynamic connectivity, component counting, or equivalence merging. Accounts Merge, Number of Connected Components, and redundant connection problems often benefit from DSU.
What Structure means here
In BASIC, the Structure step is where you state the invariant, helper contract, or control-flow skeleton before coding. For Union-Find, that matters because the pattern only becomes useful once the candidate is explicit about what is being tracked, reduced, or preserved.
Interview move
A strong move is to make the plan visible before full execution. In this pattern family, say out loud what representation makes the problem easier: the map entry, the pointer invariant, the recursion contract, the queue contents, or the DP state. That keeps the implementation attached to a reason.
Common miss
The miss is using DSU without being clear on what each parent relation represents or when path compression matters. BASIC reduces that risk because the stage sequence forces you to earn the implementation instead of jumping straight into it.
BASIC prompt
“Given that this looks like Union-Find, what is the simplest way to state the invariant, helper contract, or control-flow skeleton before coding?”