Total a basket that came off a queue
Order lines arrive from a message queue and the payload is not always clean: a line can be missing entirely, and quantities have been seen at zero.
- A missing line contributes nothing and must not stop the sum.
- A line with a quantity of zero or less contributes nothing either.
- The total is in minor units.
orderTotal(lines: list<Line?>) → int
C++ needs a compiler and Drill does not host one yet, so this page is the reference rather than an exercise: the problem, worked examples, and the solution in full. To type it out, the same problem runs in Python.
Where you start
int orderTotal(std::vector<std::optional<Line>> lines) {
}Worked examples
| Call | Result |
|---|---|
orderTotal(std::vector<std::optional<Line>>{std::optional<Line>(Line{std::string("A"), 2, 100}), std::optional<Line>(Line{std::string("B"), 3, 50})}) | 350 |
orderTotal(std::vector<std::optional<Line>>{std::optional<Line>(Line{std::string("A"), 1, 10}), std::nullopt, std::optional<Line>(Line{std::string("C"), 2, 5})}) | 20 |
orderTotal(std::vector<std::optional<Line>>{std::optional<Line>(Line{std::string("A"), 0, 999}), std::optional<Line>(Line{std::string("B"), -1, 999})}) | 0 |
orderTotal(std::vector<std::optional<Line>>{}) | 0 |
Hint
Guard inside the loop, not before it. One bad line should not cost you the rest.
Reference solution in C++
int orderTotal(std::vector<std::optional<Line>> lines) {
int total = 0;
for (const auto& l : lines) {
if (!l.has_value() || l->qty <= 0) continue;
total += l->qty * l->unitPrice;
}
return total;
}