Array Rotation and Reversal Challenges Quiz Quiz

Explore essential concepts and problem-solving techniques related to array rotation and reversal operations. This quiz offers practical scenarios to test your understanding of in-place rotations, reversal algorithms, cyclic shifts, and common pitfalls in array manipulation.

1. Rotating an Array to the Right

   Given the array [1, 2, 3, 4, 5], what is the result after rotating it to the right by 2 positions?

   1. 3, 4, 5, 1, 2
   2. 5, 1, 2, 3, 4
   3. 2, 3, 4, 5, 1
   4. 4, 5, 1, 2, 3

   Explanation: Rotating the array to the right by 2 positions moves every element 2 steps forward, with the last two wrapping around to the front. This results in [4, 5, 1, 2, 3]. The option 3, 4, 5, 1, 2 represents a right rotation by 3. The option 2, 3, 4, 5, 1 is a left rotation by 1, and 5, 1, 2, 3, 4 is a right rotation by 1. Hence, only the first option is correct.

2. In-place Array Reversal

   If you reverse the array [7, 0, 8, 9] in place, what will be the resulting array?

   1. 9, 8, 7, 0
   2. 8, 9, 0, 7
   3. 7, 9, 8, 0
   4. 9, 8, 0, 7

   Explanation: Reversing an array in place simply flips the elements from the ends toward the center. The reversed version of [7, 0, 8, 9] is [9, 8, 0, 7]. The option 9, 8, 7, 0 has swapped two middle elements incorrectly. The option 8, 9, 0, 7 does not fully reverse the array, and 7, 9, 8, 0 incorrectly positions the elements. Only '9, 8, 0, 7' reflects the true reversal.

3. Identifying the Reversed Segment

   In the array [2, 5, 4, 3, 9], which subarray has been reversed assuming only one contiguous segment was reversed in an originally sorted array?

   1. 5, 4, 3
   2. 2, 5
   3. 4, 3, 9
   4. 3, 9

   Explanation: The segment [5, 4, 3] appears in the correct sorted position if one contiguous reversal is allowed, turning [2, 3, 4, 5, 9] into [2, 5, 4, 3, 9]. The choice 2, 5 does not reflect a reversed segment in the middle. 4, 3, 9 spans the end incorrectly, and 3, 9 is too short. Only 5, 4, 3 represents the likely reversed segment affecting sort order.

4. Minimum Rotations for Sorted Array

   What is the minimum number of left rotations required to convert [8, 9, 1, 2, 3] into a sorted ascending array?

   1. 2
   2. 4
   3. 3
   4. 1

   Explanation: A left rotation shifts all elements left, moving the first element to the end. Applying two left rotations: [8, 9, 1, 2, 3] becomes [1, 2, 3, 8, 9], which is sorted. Three rotations would result in [2, 3, 8, 9, 1] and four in [3, 8, 9, 1, 2]. Only one rotation results in [9, 1, 2, 3, 8]. Thus, two rotations are required for sorting.

5. Error in Reverse Algorithm

   If an array reversal function swaps only adjacent elements once, such as [6, 7, 8] resulting in [7, 6, 8], what key operation is missing in the reversal algorithm?

   1. Swapping elements from both ends towards the center
   2. Incrementing each element after a swap
   3. Rotating the array by its length
   4. Sorting the array before reversal

   Explanation: For proper reversal, the algorithm should swap elements symmetrically from outer ends inwards. Only swapping adjacent pairs as in [7, 6, 8] is insufficient. Rotating the array by its length returns it to the original state, not reversed. Sorting before reversal is unnecessary, and incrementing elements after swapping does not achieve reversal. The missing step is swapping from both ends.