Code reviewHardcr-g260

Subject Comparator violationsLevel Senior–Staff~25 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

Review this Java comparator used to sort tasks by priority then by an int weight.

Tasks come from an upstream service and weights/priorities can be any 32-bit int, including large magnitudes. The team reports sporadic `IllegalArgumentException: Comparison method violates its general contract!` from `TimSort`, but only on certain shards.

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Code to reviewjava

1class Task {2    int priority;   // any 32-bit int from upstream3    int weight;     // any 32-bit int from upstream4}5 6void schedule(List<Task> tasks) {7    tasks.sort((a, b) -> {8        if (a.priority != b.priority) {9            return a.priority - b.priority;   // ascending by priority10        }11        return b.weight - a.weight;           // descending by weight12    });13    run(tasks);14}

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