AOC Day 7 part 2

day7pt2.py

filename = '7.csv'
with open(filename, 'r') as f:
    for line in f:
        positions = map(int, line.split(','))


def build_costs(max_num):
    costs = {}
    for i in range(max_num):
        if i == 0:
            costs[0] = 0
        else:
            costs[i] = costs[i - 1] + i
    return costs


def calc_fuel(val):
    req_fuel = 0
    for p in positions:
        req_fuel += costs[abs(p - val)]
    return req_fuel


costs = build_costs(max(positions) + 1)
avg = int(round(sum(positions) / float(len(positions))))
curr_fuel = calc_fuel(avg)
base = avg

min_found = False
while not min_found:
    lt_fuel = calc_fuel(avg - 1)
    rt_fuel = calc_fuel(avg + 1)
    if rt_fuel < curr_fuel:
        if lt_fuel < rt_fuel:
            curr_fuel, base = lt_fuel, base - 1
        else:
            curr_fuel, base = rt_fuel, base + 1
    elif lt_fuel < curr_fuel:
        curr_fuel, base = lt_fuel, base - 1
    else:
        min_found = True

print(curr_fuel)