adjacent_product.cpp

int adjacentElementsProduct(std::vector<int> inputArray) {
    auto begin = std::begin(inputArray);
    auto end   = std::end(inputArray);

    if (inputArray.size() < 2) {
        // what do we return in this instance??
        // is the input gauranteed to be at least 2 elements?
        return 0;
    }
    
    int answer = *begin;
    begin = std::next(begin);
  
    int last;
    
    answer *= *begin;
    last = *begin;
    begin = std::next(begin);
    
    for (; begin != end; begin = std::next(begin)) {
        int test = *begin * last;
        if (test > answer) {
            answer = test;
        }
        last = *begin;
    }
    
    return answer;
}