Array Rotation Techniques in DSA C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is array rotation?

Array rotation means shifting the elements of an array to the left or right by a certain number of positions, wrapping around the elements that go past the end.

beginner

Explain the difference between left rotation and right rotation of an array.

Left rotation moves elements towards the start of the array, pushing the first elements to the end. Right rotation moves elements towards the end, pushing the last elements to the front.

intermediate

What is the time complexity of rotating an array by one position using the naive method?

The naive method shifts elements one by one, so rotating by one position takes O(n) time, where n is the array size.

intermediate

Describe the reversal algorithm for array rotation.

The reversal algorithm rotates an array by reversing parts of the array: first reverse the first part, then reverse the second part, and finally reverse the whole array to get the rotated array.

intermediate

Why is the reversal algorithm more efficient than the naive rotation method?

The reversal algorithm rotates the array in O(n) time with only three reversals, avoiding multiple shifts and reducing the number of operations.

What happens to the elements when you rotate an array to the left by 2 positions?

A The first two elements move to the end, and the rest shift left

B The last two elements move to the front, and the rest shift right

C All elements reverse their order

D The array remains unchanged

Left rotation by 2 moves the first two elements to the end, shifting the rest left.

Which algorithm rotates an array by reversing parts of it?

A Naive rotation

B Reversal algorithm

C Bubble sort

D Selection sort

The reversal algorithm rotates an array by reversing segments and then the whole array.

What is the time complexity of the reversal algorithm for rotating an array?

A O(n^2)

B O(n log n)

C O(n)

D O(1)

The reversal algorithm completes rotation in linear time O(n).

If you rotate an array of size 5 to the right by 1, where does the last element go?

A It moves to the middle

B It is removed

C It stays at the last position

D It moves to the front (index 0)

Right rotation by 1 moves the last element to the front.

Which method is less efficient for large arrays when rotating multiple positions?

A Naive rotation by shifting one element at a time

B Reversal algorithm

C Using extra array to copy elements

D No rotation

Naive rotation shifts elements one by one, which is inefficient for large arrays.

Explain how to rotate an array to the left by d positions using the reversal algorithm.

Think about reversing parts of the array step by step.

Describe the difference between naive rotation and the reversal algorithm in terms of steps and efficiency.

Compare how many operations each method uses.