from timeit import timeit
from math import floor

# 1. Can you implement another optimised function (sum_even_numbers2) using purely native python?
#    Can you timeit to show it's faster and describe why it is.
#    Can you also state if there are any pros or cons to how it is implemented?

# 2. Can you implement another optimised function (sum_even_numbers3) using third party packages?
#    Can you timeit to show it's faster and describe why it is.
#    Can you also state if there are any pros or cons to how it is implemented?

def sum_even_numbers1(numbers: list[int]) -> int:
    total = 0
    for num in numbers:
        if floor(num/2) == num/2:
            total += num
    return total

# Floating point calculation is not required
# Only one division required
# float required 32byte, memory heavy
def sum_even_numbers2(numbers: list[int]) -> int:
    total = 0
    for num in numbers:
        if num%2 == 0:
            total += num
    return total

# needs to call that function from memory
def sum_even_numbers3(numbers: list[int]) -> int:
    return sum(filter(lambda x: x > 0 and x%2 == 0, numbers))

# generators are often faster
def sum_even_numbers4(numbers: list[int]) -> int:
    return sum(num for num in numbers if not num%2)

# generators without if statements are almost always faster
def sum_even_numbers5(numbers: list[int]) -> int:
    return sum(n * (not n&1) for n in numbers)

# the max() function of python is written in C, and maths are even faster than a loop
def sum_even_numbers6(numbers: list[int]) -> int:
    maxi = max(numbers)
    return maxi//2 * (maxi//2 + 1)

# why keeping two divisions?
def sum_even_numbers7(numbers: list[int]) -> int:
    return (maxi := max(numbers) >> 1) * (maxi + 1)

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