Array reversal in O( log n) time.

Question

Is reversing an array in O( log n) possible? I know it's possible with an O( log n) time lookup, but I don't know if it's possible with an O(1) time lookup. I also don't know if there is a "easy" solution with an O( log n) time lookup, because mine is quite complicated ( +- 1000 lines of code).

Answer 1

Hi John!

Reversing an array in O(log n) time complexity is not possible. The reason for this is that reversing an array involves swapping elements, and to perform a swap operation for each element in an array, you would need to traverse the entire array at least once. This results in a linear time complexity.

The O(log n) time complexity is often associated with algorithms that divide the problem into smaller subproblems and solve each subproblem independently. Reversing an array requires dealing with every element, making it inherently O(n).

If there are any claims stating O(log n) complexity for array reversal, they might be based on a misunderstanding or misinterpretation. Reversing an array fundamentally requires linear time complexity due to the need to visit each element.

Best,

J