blue_red_cost.py

def minimum_cost_array(red, blue, blue_cost):
    assert len(red) == len(blue), f"red and blue lines have different sizes"
    result = [0]
    is_blue = False
    for r, b in zip(red, blue):
        cost_blue = b if is_blue else b + blue_cost
        cost_red = r
        if cost_blue <= cost_red:
            is_blue = True
            result.append(result[-1] + cost_blue)
        else:
            is_blue = False
            result.append(result[-1] + cost_red) 
    return result


red = [2,3,4]
blue = [3,1,1]
blue_cost = 2

actual = minimum_cost_array(red, blue, blue_cost) 
expected = [0, 2, 5, 6]
assert actual == expected, f"{actual} != {expected}"
print("ok")