Totals per category
A ledger groups every sale under its category so each bucket shows a single sum.
- Add the amounts of every sale under the same category.
- Every category that appears earns an entry in the result.
- The result is one running total per category.
sumPerCategory(sales: list<Sale>) → map<string, 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
std::map<std::string, int> sumPerCategory(std::vector<Sale> sales) {
}Worked examples
| Call | Result |
|---|---|
sumPerCategory(std::vector<Sale>{Sale{std::string("food"), 10}, Sale{std::string("food"), 15}}) | std::map<std::string, int>{{std::string("food"), 25}} |
sumPerCategory(std::vector<Sale>{Sale{std::string("a"), 3}, Sale{std::string("b"), 4}, Sale{std::string("a"), 5}}) | std::map<std::string, int>{{std::string("a"), 8}, {std::string("b"), 4}} |
sumPerCategory(std::vector<Sale>{Sale{std::string("x"), 1}}) | std::map<std::string, int>{{std::string("x"), 1}} |
sumPerCategory(std::vector<Sale>{Sale{std::string("p"), 0}, Sale{std::string("q"), -2}}) | std::map<std::string, int>{{std::string("p"), 0}, {std::string("q"), -2}} |
Hint
Aggregate into a map keyed by category, adding each amount as you go.
Reference solution in C++
std::map<std::string, int> sumPerCategory(std::vector<Sale> sales) {
std::map<string, int> result;
for (const auto& s : sales) result[s.category] += s.amount;
return result;
}