10 free days · Days 1–10 included
- Solve challenge
DAY 01
The Receipt That Must Balance
Easy · Integer arithmetic · money · 6 test cases
Turn a shopping basket into an exact receipt without losing a cent.
- Solve challenge
DAY 02
Restock Before the Shelf Is Empty
Easy · Conditions · records · 6 test cases
Produce a purchasing list from real stock levels and reorder thresholds.
- Solve challenge
DAY 03
A Parking Meter With Boundaries
Medium · Rounding · tiered pricing · 8 test cases
Implement a tariff where one minute can change the bill.
- Solve challenge
DAY 04
A Sensor Feed You Can Trust
Easy · Types · validation · 6 test cases
Separate usable temperature readings from corrupt input.
- Solve challenge
DAY 05
Stop a Burst Without Stopping Everyone
Medium · Loops · state machines · 6 test cases
Simulate a token-bucket rate limiter for an API.
- Solve challenge
DAY 06
Clear the Backorder Queue
Medium · Nested loops · FIFO queues · 6 test cases
Distribute orders across daily packing capacity without skipping a customer.
- Solve challenge
DAY 07
The Cash Drawer Is Not Unlimited
Hard · Search · bounded dynamic programming · 7 test cases
Find exact change when the familiar greedy choice can fail.
- Solve challenge
DAY 08
A PIN Policy With a Catch
Easy · Strings · adjacent values · 8 test cases
Flag weak access PINs with explicit, explainable reasons.
- Solve challenge
DAY 09
Measurements From Three Suppliers
Medium · Text parsing · exact unit conversion · 6 test cases
Normalize dimensions while rejecting ambiguous or malformed labels.
- Solve challenge
DAY 10
Compress the Missing Ticket Numbers
Easy · Lists · runs of consecutive values · 6 test cases
Make a long list of missing tickets readable without hiding a gap.
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