rust / LEVEL 3
THEORY / RETRIEVAL
After counting U unique values, a min-heap of size K keeps the weakest current winner at its root. Each candidate costs O(log K), avoiding an O(U log U) full sort when K is small. Final K results are then sorted for the public output contract.
Rust's `BinaryHeap` is a max-heap. `Reverse` can invert tuple ordering, but every tuple field participates. Here lower frequency is worse, and for equal frequency the larger numeric value is worse because output prefers smaller values.
CHECKPOINT
02 / IMPLEMENTATION
Return up to k (value, frequency) pairs ordered by frequency descending and value ascending. Use a heap bounded by k after counting; k=0 returns empty and k greater than the unique count returns every value.
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