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  1. Triple sum
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Triple sum

  • torexed
     + 0 comments

    Used set to remove duplicates and create order. Put data back into vectors to retrieve indices for upper bound checks.

    // Complete the triplets function below.
long triplets(vector<int> a, vector<int> b, vector<int> c) {
    long result = 0;
    std::set<int> setA{a.begin(), a.end()};
    std::set<int> setB{b.begin(), b.end()};
    std::set<int> setC{c.begin(), c.end()};
    
    std::vector<int> orderedA {setA.begin(), setA.end()};
    std::vector<int> orderedC {setC.begin(), setC.end()};
    
    for (const auto& itemB : setB)
    {
        auto idxA = std::upper_bound(orderedA.begin(), orderedA.end(), itemB);
        auto idxC = std::upper_bound(orderedC.begin(), orderedC.end(), itemB);
        auto aDiff = idxA - orderedA.begin();
        auto cDiff = idxC - orderedC.begin();
        result += aDiff * cDiff;
    }
    
    return result;
}