1) про единицы
a = [1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1] => 5
a = [1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1] => 6
[0,0,0,1,1,1,0,0,0,1,0,1,1,1] => 4
[1,0,1,0,1,0,1,0] => 2
[1,0,1,0,1,1] -> 3

возможно удалить один элемент
ans = 5

def solve(arr):
    index = 0
    n = len(arr)
    max_count = 0
    current_count = 0
    null_deleted = False
    count_after_null = 0

    while index < n:
        if arr[index] == 1:
            if current_count == 0 and count_after_null:
                current_count += count_after_null
                count_after_null = 0
-->         else:
                current_count += 1

            if null_deleted:
                count_after_null += 1
        else:
            if current_count == 0:
                index += 1
                count_after_null = 0
                continue
            if null_deleted:
                max_count = max(max_count, current_count)
                current_count = 0
                null_deleted = False
            else:
                null_deleted = True
        index += 1

    return max(current_count, max_count)