Bucket some readings
A chart needs counts per band rather than raw readings — how many orders fell between 0 and 9, 10 and 19, and so on.
- Readings are never negative.
- A bucket is named by the value it starts at, written as a string: "0", "10", "20".
- Buckets with nothing in them do not appear.
- A bucket size of zero or less gives an empty result.
histogram(values: list<int>, bucketSize: int) → 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> histogram(std::vector<int> values, int bucketSize) {
}Worked examples
| Call | Result |
|---|---|
histogram(std::vector<int>{0, 5, 10, 15, 23}, 10) | std::map<std::string, int>{{std::string("0"), 2}, {std::string("10"), 2}, {std::string("20"), 1}} |
histogram(std::vector<int>{9, 10}, 10) | std::map<std::string, int>{{std::string("0"), 1}, {std::string("10"), 1}} |
histogram(std::vector<int>{1, 2, 3}, 1) | std::map<std::string, int>{{std::string("1"), 1}, {std::string("2"), 1}, {std::string("3"), 1}} |
histogram(std::vector<int>{1, 2}, 0) | std::map<std::string, int>{} |
Hint
Integer-divide by the bucket size, multiply back, and that is the bucket name.
Reference solution in C++
std::map<std::string, int> histogram(std::vector<int> values, int bucketSize) {
std::map<string, int> result;
if (bucketSize <= 0) return result;
for (int v : values) {
result[std::to_string(v / bucketSize * bucketSize)]++;
}
return result;
}