Why is the time complexity of python's list.append() method O(1)?

Question

As seen in the documentation for TimeComplexity, Python\'s list type is implemented is using an array.

So if an array is being used and we do a few appe

Answer 1

This is very easy.

We can calculate this by accumulating the total time of appending n elements into an arraylist and divide it by n.

Firstly, we need to relocate log(n) times, and every relocation is doubled by 2.So we have a proportional series whose ratio is 2, and the length is log(n).

The sum of a proportional series is a(1-r^n)/(1-r) So the total time of relocation is (1-n)/(1-2)=n The time complexity would be n/n=1.