haunted.cpp

int matrixElementsSum(std::vector<std::vector<int>> matrix) {
    int price  = 0;
    int width  = matrix[0].size();
    int height = matrix.size(); 
    std::vector<std::pair<int, int>> haunted {};
    
    auto flat = std::accumulate(std::begin(matrix), std::end(matrix), std::vector<int>(),
                                [](auto collector, auto row) {
        collector.insert(std::end(collector), std::begin(row), std::end(row));
        return collector;
    });
    
    for (auto itr = std::begin(flat); itr != std::end(flat); ++itr) {
        int row    = std::distance(std::begin(flat), itr) % width;
        int column = std::distance(std::begin(flat), itr) / height;
        int cost   = *itr;
        
        if (cost == 0) {
            haunted.emplace_back(row, column);
            continue;
        }
        
        bool is_haunted = false;
        for (int i = 0; i < column; ++i) {
            if (std::find(std::begin(haunted), std::end(haunted),
                          std::make_pair(row, i)) != std::end(haunted)) {
                is_haunted = true;
            }
        }
        
        if (!is_haunted) price += cost;
    }
    
    return price;
}