import sys
from itertools import combinations
from lib import *

TOP_FLOOR = 3
part_1 = False
if part_1:
    #        g0, c0, g1, c1, ...         elevator 
    state = [0, 0, 1, 2, 1, 2, 1, 2, 1, 2, 0]
else:
    state = [0, 0, 0, 0, 0, 0, 1, 2, 1, 2, 1, 2, 1, 2, 0]


def is_state_valid(state):
    for floor in range(0, TOP_FLOOR + 1):
        gens_on_floor = [i // 2 for i in range(0, len(state) - 1, 2) if state[i] == floor]
        chips_on_floor = [i // 2 for i in range(1, len(state) - 1, 2) if state[i] == floor]
        if len(gens_on_floor) > 0:
            for c in chips_on_floor:
                if not c in gens_on_floor:
                    return False
    return True

assert is_state_valid([0, 0, 1, 2, 1, 2, 1, 2, 1, 2, 0]) == True
assert is_state_valid([0, 0, 1, 0, 1, 2, 1, 2, 1, 2, 0]) == False


def is_end_state(state):
    return all([o == TOP_FLOOR for o in state])

assert is_end_state([0, 0, 1, 0, 1, 2, 1, 2, 1, 2, 0]) == False
assert is_end_state([3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3]) == True


def next_states(state):
    floor = state[-1]
    objects_on_floor = [i for i in range(len(state) - 1) if state[i] == floor]

    nstates = []
    for o in objects_on_floor:
        if floor > 0:
            nstate = list(state)
            nstate[o] -= 1
            nstate[-1] -= 1
            nstates.append(nstate)
        if floor < TOP_FLOOR:
            nstate = list(state)
            nstate[o] += 1
            nstate[-1] += 1
            nstates.append(nstate)

    for os in combinations(objects_on_floor, 2):
        if floor > 0:
            nstate = list(state)
            for o in os:
                nstate[o] -= 1
            nstate[-1] -= 1
            nstates.append(nstate)
        if floor < TOP_FLOOR:
            nstate = list(state)
            for o in os:
                nstate[o] += 1
            nstate[-1] += 1
            nstates.append(nstate)
    return nstates


states = [state]
for step in range(1000):
    nstates = []
    seen = set()
    for state in states:

        statet = tuple(state)
        if statet in seen:
            continue
        seen.add(statet)

        for nstate in next_states(state):
            if not is_state_valid(nstate):
                continue
            if is_end_state(nstate):
                print(step + 1)
                sys.exit(0)
            nstates.append(nstate)

    # Keep search space manageable with pretty bad pruning.
    nstates.sort(reverse=True)
    states = nstates[:20000]