Turn the floor plan a quarter turn
A layout tool rotates a square plan ninety degrees clockwise so it fits the room the other way round.
- The plan is square.
- The top row becomes the right-hand column, read downwards.
- An empty plan comes back empty.
rotateClockwise(plan: list<list<int>>) → list<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
std::vector<std::vector<int>> rotateClockwise(std::vector<std::vector<int>> plan) {
}Worked examples
| Call | Result |
|---|---|
rotateClockwise(std::vector<std::vector<int>>{std::vector<int>{1, 2}, std::vector<int>{3, 4}}) | std::vector<std::vector<int>>{std::vector<int>{3, 1}, std::vector<int>{4, 2}} |
rotateClockwise(std::vector<std::vector<int>>{std::vector<int>{1, 2, 3}, std::vector<int>{4, 5, 6}, std::vector<int>{7, 8, 9}}) | std::vector<std::vector<int>>{std::vector<int>{7, 4, 1}, std::vector<int>{8, 5, 2}, std::vector<int>{9, 6, 3}} |
rotateClockwise(std::vector<std::vector<int>>{std::vector<int>{1}}) | std::vector<std::vector<int>>{std::vector<int>{1}} |
rotateClockwise(std::vector<std::vector<int>>{}) | std::vector<std::vector<int>>{} |
Hint
The cell at row r, column c lands at row c, column (last - r). Building a fresh grid is easier to get right than shuffling in place.
Reference solution in C++
std::vector<std::vector<int>> rotateClockwise(std::vector<std::vector<int>> plan) {
int n = static_cast<int>(plan.size());
std::vector<std::vector<int>> turned;
for (int r = 0; r < n; r++) {
std::vector<int> row;
for (int c = 0; c < n; c++) row.push_back(plan[n - 1 - c][r]);
turned.push_back(row);
}
return turned;
}