advent_of_code/2021/7/7_2.py

#!/usr/bin/env python
# 2021 - Advent Of Code - 7 part 2

def parse_file(file):
    with open(file, encoding="utf-8") as f:
        line = f.readline()

    list_state = [int(x) for x in line.split(',')]

    return list_state


def sum_n(n):
    return int(n*(n+1) / 2)


# init_state = parse_file('input_example.txt')
init_state = parse_file('input.txt')
nb_crabs = len(init_state)
print(f'Initial state with {nb_crabs} crabs: {init_state}')

max_h = max(init_state)
print(f'maximum horizontal position is {max_h}')
all_diff = [0] * max_h

min_fuel = sum_n(max_h) * nb_crabs
min_fuel_pos = 0
for m in range(max_h):
    list_diff = [sum_n(abs(m-x)) for x in init_state]
    if sum(list_diff) < min_fuel:
        min_fuel = sum(list_diff)
        min_fuel_pos = m

    all_diff[m] = list_diff

print(f'min fuel {min_fuel} for position {min_fuel_pos}')