day7.py

def calculate_minimum_spent_fuel_constant(crab_positions: list):
    min_pos = min(crab_positions)
    max_pos = max(crab_positions)

    min_fuel_spent = None
    optimal_position = None
    for pos in range(min_pos, max_pos):
        fuel_spent = 0
        for crab_pos in crab_positions:
            fuel_spent += abs(crab_pos - pos)
        if min_fuel_spent == None or min_fuel_spent > fuel_spent:
            min_fuel_spent = fuel_spent
            optimal_position = pos
    
    print(f'Optimal position found at {optimal_position} with fuel spent {min_fuel_spent}')
    return min_fuel_spent

def sum_up(number):
    sum = 0
    for x in range(1, number+1):
        sum += x
    return sum

def calculate_minimum_spent_fuel_increasing(crab_positions: list):
    min_pos = min(crab_positions)
    max_pos = max(crab_positions)

    min_fuel_spent = None
    optimal_position = None
    fuel_dictionary = {} # use dictionary to store calculated fuel consumption
    for pos in range(min_pos, max_pos):
        fuel_spent = 0
        for crab_pos in crab_positions:
            distance = abs(crab_pos - pos)
            if distance in fuel_dictionary:
                # if consumption has been calculated before use this value
                fuel_consumption = fuel_dictionary[distance]
            else:
                # otherwise calculate and store value
                fuel_consumption = sum_up(distance)
                fuel_dictionary[distance] = fuel_consumption
            fuel_spent += fuel_consumption
        if min_fuel_spent == None or min_fuel_spent > fuel_spent:
            min_fuel_spent = fuel_spent
            optimal_position = pos
    
    print(f'Optimal position found at {optimal_position} with fuel spent {min_fuel_spent}')
    return min_fuel_spent

def test_crab_movement():
    test_crab_data = [16,1,2,0,4,2,7,1,2,14]

    minmum_spent_fuel = calculate_minimum_spent_fuel_constant(test_crab_data)
    assert minmum_spent_fuel == 37, 'should be 37'

    minmum_spent_fuel = calculate_minimum_spent_fuel_increasing(test_crab_data)
    assert minmum_spent_fuel == 168, 'should be 168'

def main():
    f = open('day7_input.txt', 'r')
    lines = f.readlines()
    crab_data = list(map(int,lines[0].strip().split(',')))

    # part 1
    minmum_spent_fuel = calculate_minimum_spent_fuel_constant(crab_data)
    print(f'Result for part 1 is {minmum_spent_fuel}')

    # part 2
    minmum_spent_fuel = calculate_minimum_spent_fuel_increasing(crab_data)
    print(f'Result for part 2 is {minmum_spent_fuel}')

if __name__ == "__main__":
    main()