It’s amortized O(1), not O(1). Let’s say the list reserved size is 8 elements and it doubles in size when space runs out. You want to push 50 elements. The first 8 elements push in O(1). The nineth triggers reallocation and 8 copies, followed by an O(1) push. The next 7 push in O(1). The … Read more
Amortized complexity is the total expense per operation, evaluated over a sequence of operations. The idea is to guarantee the total expense of the entire sequence, while permitting individual operations to be much more expensive than the amortized cost. Example: The behavior of C++ std::vector<>. When push_back() increases the vector size above its pre-allocated value, … Read more
Amortized analysis doesn’t naively multiply the number of invocations with the worst case for one invocation. For example, for a dynamic array that doubles in size when needed, normal asymptotic analysis would only conclude that adding an item to it costs O(n), because it might need to grow and copy all elements to the new … Read more