The middle of a set of readings
A latency report quotes the median rather than the mean, because one slow request should not move the headline number.
- Sort first — the readings arrive in whatever order they were logged.
- An odd count has a single middle value.
- An even count takes the average of the two in the middle, which may be a half.
- No readings at all gives 0.
medianValue(values: list<int>) → float
Java 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
double medianValue(List<Integer> values) {
}Worked examples
| Call | Result |
|---|---|
medianValue(Main.<Integer>ls(3, 1, 2)) | 2.0 |
medianValue(Main.<Integer>ls(1, 2, 3, 4)) | 2.5 |
medianValue(Main.<Integer>ls(7)) | 7.0 |
medianValue(Main.<Integer>ls()) | 0.0 |
Hint
After sorting, the two middles for an even count sit at n/2 - 1 and n/2.
Reference solution in Java
double medianValue(List<Integer> values) {
if (values.isEmpty()) return 0.0;
List<Integer> s = new ArrayList<>(values);
Collections.sort(s);
int n = s.size(), mid = n / 2;
return n % 2 == 1 ? s.get(mid) : (s.get(mid - 1) + s.get(mid)) / 2.0;
}