Collapse repeats in a sorted feed
A sorted export repeats an id whenever a row was touched twice. The importer wants each id once, still in order.
- The input arrives sorted ascending, so equal values are always adjacent.
- Each distinct value survives once, in the order it first appeared.
- An empty feed comes back empty.
dedupeSorted(ids: list<int>) → list<int>
Go 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
func dedupeSorted(ids []int) []int {
}Worked examples
| Call | Result |
|---|---|
dedupeSorted([]int{1, 1, 2, 3, 3, 3}) | []int{1, 2, 3} |
dedupeSorted([]int{1, 2, 3}) | []int{1, 2, 3} |
dedupeSorted([]int{5, 5, 5, 5}) | []int{5} |
dedupeSorted([]int{}) | []int{} |
Hint
Because it is sorted you only ever need to compare against the value you kept last. Walk forward and keep a value only when it differs from that one.
Reference solution in Go
func dedupeSorted(ids []int) []int {
out := []int{}
for _, id := range ids {
if len(out) == 0 || out[len(out)-1] != id {
out = append(out, id)
}
}
return out
}