Questions
19 of 19
How do you rotate an array by k positions? (In-place vs extra space)
Difficulty: 3/10
Array Rotation
For right rotation by k positions, first reduce k using k modulo n. An efficient in-place approach uses three reversals: reverse the entire array, reverse the first k elements, then reverse the remaining elements.
javascript
- 1
Time complexity: O(n).
- 2
Extra space: O(1) for the reversal approach.
- 3
An extra-array approach is simpler but requires O(n) additional space.
- 4
For very large k, k % n avoids unnecessary rotations.
- 5
The direction of rotation must be defined clearly.
Follow-up Questions
- How would you rotate left by k?
- Can you solve rotation using the cyclic replacement method?