In the worst case while appending an element(inserting at end) array can be full. So a new array is created and n elements are copied from this array to the new array.
I read in literature that worst case time complexity of this operation is O(1), why so? shouldn't it be O(n)?
I did read this question. But did not make any sense to me!
The operation itself is O(n).
If you get the average operations per element, you get O(1), this is the amortized cost.
See more at http://en.wikipedia.org/wiki/Amortized_analysis
I see it the same way that you do.
If it was a List, then it was O(1) to add an element at the end.
But in the case of an array, if it´s full you need to create a new one, copy all the elements in the old array, and then add the new element.
For me it´s O(n) too.
In case of static list/array the time complexity must be O(n), but in case of dynamic array/list, the time complexity comes O(1) because in dynamic array there is a facility to allocate extra memory for the append operation .
