问题
In Python, if we need to find the maximum element from the list. We use :
>>>max(listname) to get the maximum number from the list.
Time Complexity : O(1)
If we use C/C++,
we need to iterate over the loop and get the max.
Time Complexity: O(n) or O(n square)
Hence, does the time complexity changes over the programming language?
回答1:
No. max(listname) is always O(N) where N is the length of listname (*). This is just by definition of complexity - because the iteration has to happen somewhere - maybe in your code (in case of your C/C++), or maybe in library code (in case of Python).
Sometimes we ignore some complexity, usually because it is beneath our notice; for example, x * y in Python (with x and y being integers) is actually not O(1), because x and y are of arbitrary length in Python, and the * operation thus does execute in loops, but we do simplify and treat it as O(1), as it is most often the case that the integers are of small enough size for it not to matter.
The choice of programming language only matters inasmuch as it affects our perception of what we can ignore; but it does not actually change the time complexity.
*) it is only O(N) in case N is proportional to input size; it is O(1) if it is known in advance, or limited. For example, lst = read_list(); m = max(lst) is O(N), but lst = [1, 2, 3, 4]; m = max(lst) is O(1), as is lst = read_list(); lst = lst[:4]; m = max(lst).
来源：https://stackoverflow.com/questions/53919758/does-time-complexity-changes-as-we-change-our-programming-language