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Practice0:00
Exact Change · D1

Make exactly 47 in the fewest coins.

Tap coins to add them; tap a chosen coin to remove it. Greedy largest-first is a trap on these denominations — the fewest-coin answer is a DP.
Practice — no rating pressure. Get as close to the optimum as you can; each play teaches the pattern.
Coins used
0
Sum
0 / 47
Coins
About this puzzle

Exact Change — practice the decision, scored against the optimum

What does the Exact Change puzzle teach?

Greedy 'largest coin first' isn't optimal for arbitrary denominations — minimum-coin change is a DP.

Why do interviews ask about this?

Coin change is the DP interview staple — greedy fails for arbitrary denominations; know when to reach for dynamic programming.

How is it scored?

The engine computes the provably-optimal answer for the exact instance you played (dynamic programming, shortest-path, or exhaustive search — never a heuristic) and scores your attempt as a percentage of it. No login needed to see your score.