heaven in the tea

"""

You get a list of numbers.

Find the longest stretch of numbers (contiguous) whose sum is even.

Return the length. If none exist, return 0.

"""

from typing import List

def longest_even_sum_subarray(nums: List[int]) -> int:

    if not nums:

        return 0

    check_list = []

    for start in range(len(nums)):

        current_sum = 0

        best_length = 0

        for end in range(start, len(nums)):

            current_sum += nums[end]

            if current_sum % 2 == 0:

                best_length += 1

        check_list.append(best_length)

    return max(check_list)

def run_manual_examples() -> None:

    test_cases = [

        ([1, 2, 3, 4], 4),

        ([1, 3, 5], 0),

        ([2, 2, 2], 3),

        ([1], 0),

        ([2], 1),

        ([1, 2, 2, 1], 4),

    ]

    print("Running manual test cases...\n")

    for nums, expected in test_cases:

        result = longest_even_sum_subarray(nums)

        print(f"Input: {nums}")

        print(f"Expected: {expected}, Got: {result}")

        print("-" * 40)

def main():

    print("Longest Even-Sum Subarray Checker")

    user_input = input("Enter numbers: ").strip()

    if user_input == "":

        run_manual_examples()

    else:

        try:

            nums = [int(x) for x in user_input.split()]

        except ValueError:

            print("Invalid input.")

            return

        result = longest_even_sum_subarray(nums)

        print(f"\nResult: {result}")

if __name__ == "__main__":

    main()