What is the time complexity of insertion, search, read, and delete operations in an array in the worst and average cases?

For a standard array in iOS (e.g., NSArray or NSMutableArray), the approximate characteristics of operations are as follows:

• Insertion:

  • At the end of the array (append): average and worst case — O(1) amortized (if no reallocation is required).
  • At the beginning or middle: O(n), as elements need to be shifted.

• Search (if searching by index): O(1), since the array is indexed.

• Reading by index: O(1).

• Deletion:

  • From the end of the array: O(1).
  • From the beginning or middle: O(n), due to shifting elements.

Thus, insertion and deletion operations in the middle or beginning of the array have linear complexity, while access and insertion/deletion at the end are constant (amortized).