Push the empty slots to the end
A picking list uses zero for a line that was cancelled. The screen keeps the live lines in order and pushes the blanks to the bottom.
- Every non-zero value keeps its position relative to the others.
- All the zeros end up together at the end.
- The list comes back the same length it went in.
MoveBlanksLast(lines: list<int>) → list<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
public List<int> MoveBlanksLast(List<int> lines) {
}Worked examples
| Call | Result |
|---|---|
MoveBlanksLast(new List<int> { 0, 1, 0, 3, 12 }) | new List<int> { 1, 3, 12, 0, 0 } |
MoveBlanksLast(new List<int> { 1, 2, 3 }) | new List<int> { 1, 2, 3 } |
MoveBlanksLast(new List<int> { 0, 0 }) | new List<int> { 0, 0 } |
MoveBlanksLast(new List<int> { }) | new List<int> { } |
Hint
Keep a write index. Walk the list once copying every non-zero value to that index and advancing it; then fill what is left with zeros.
Reference solution in C#
public List<int> MoveBlanksLast(List<int> lines) {
var outList = new List<int>();
foreach (var value in lines) {
if (value != 0) outList.Add(value);
}
while (outList.Count < lines.Count) outList.Add(0);
return outList;
}