Break a list into fixed-size pieces
A bulk API takes at most a hundred records per call, so a long list has to be handed over in pieces.
- Every piece is the given size except possibly the last, which takes what is left.
- A size of zero or less gives an empty result.
- An empty input gives an empty result, not a list holding one empty piece.
chunkList(values: list<int>, perChunk: int) → list<list<int>>
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
List<List<Integer>> chunkList(List<Integer> values, int perChunk) {
}Worked examples
| Call | Result |
|---|---|
chunkList(Main.<Integer>ls(1, 2, 3, 4, 5), 2) | Main.<List<Integer>>ls(Main.<Integer>ls(1, 2), Main.<Integer>ls(3, 4), Main.<Integer>ls(5)) |
chunkList(Main.<Integer>ls(1, 2, 3, 4), 2) | Main.<List<Integer>>ls(Main.<Integer>ls(1, 2), Main.<Integer>ls(3, 4)) |
chunkList(Main.<Integer>ls(1), 5) | Main.<List<Integer>>ls(Main.<Integer>ls(1)) |
chunkList(Main.<Integer>ls(), 2) | Main.<List<Integer>>ls() |
Hint
Step the index forward by the chunk size and slice, rather than pushing one item at a time.
Reference solution in Java
List<List<Integer>> chunkList(List<Integer> values, int perChunk) {
List<List<Integer>> result = new ArrayList<>();
if (perChunk <= 0) return result;
for (int i = 0; i < values.size(); i += perChunk) {
result.add(new ArrayList<>(values.subList(i, Math.min(i + perChunk, values.size()))));
}
return result;
}