Property Combination for Group Size

Given properties (each with a capacity) in a neighborhood and a target group size, find the combination that fits the group while minimizing total capacity, breaking ties by fewest properties. A long-standing Airbnb onsite coding problem. Requirements Input: a list of properties, each with a capacity (optionally filtered to a given neighborhood); a target groupSize. Find a combination of properties whose combined capacity is at least groupSize. Priority among valid combinations: Minimize total capacity (least over-provisioning). On a tie, pick the combination using the fewest properties. Enumerate combinations with pruning; return the best combination. Notes A long-circulating Airbnb onsite coding problem (the "booking / reservation system" prompt). The algorithm is combinatorial subset search with pruning once a partial total already exceeds the best total found. The ranking order is the most common bug: minimize total capacity first, then fewest properties. Candidates routinely flip the two keys — confirm the order with the interviewer. Debug- and edge-case-heavy. Candidates consistently report running out of time on test cases after over-investing in small helper functions. Budget time to finish the main logic and tests, not polish. Edge cases: no combination reaches groupSize, exact fit, multiple combinations with identical capacity and count. Preparation Implement the subset enumeration with branch-and-bound pruning in under 25 minutes, leaving time for tests. Encode the comparator as an explicit tuple key (total_capacity, property_count) to avoid flipping the priority. Write tests for: exact fit, no valid combination, and a tie on capacity broken by count.