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from utils import open_day
from functools import cache
from dataclasses import dataclass
from itertools import count, chain
import re
@dataclass
class Node:
flow: int
neighbours: list[tuple[str, int]]
ids = {'AA': 0}
nextid = 1
def intern(n):
global nextid
if n in ids: return ids[n]
ids[n] = nextid
nextid += 1
return nextid - 1
regex = re.compile(r'^Valve (..) has flow rate=([0-9]+); tunnels? leads? to valves? (.*)$')
inp = {}
with open_day(16) as f:
for line in f:
m = regex.match(line)
assert(m)
valve, flow, neighbours = m.group(1, 2, 3)
inp[intern(valve)] = (int(flow), [intern(n) for n in neighbours.split(', ')])
nodes = {}
for valve, (flow, neighbours) in inp.items():
if valve != 0 and flow == 0: continue
actual_neighbours = []
for n in neighbours:
prev = valve
for cost in count(1):
if n == 0 or inp[n][0] != 0: break
l, r = inp[n][1]
nnext = r if l == prev else l
prev = n
n = nnext
actual_neighbours.append((n, cost))
nodes[valve] = Node(flow, actual_neighbours)
@cache
def sum_flow(open_valves):
total = 0
for i in count():
if not open_valves: break
if open_valves & 1: total += nodes[i].flow
open_valves >>= 1
return total
@cache
def recurse(open_valves=0, current=0, flow=0, time_left=30):
cflow = sum_flow(open_valves)
cnode = nodes[current]
best = flow + cflow * time_left
def check(open_valves, current, flow, time_left):
nonlocal best
new = recurse(open_valves, current, flow, time_left)
if new > best: best = new
for neighbour, cost in cnode.neighbours:
if cost >= time_left: continue
check(open_valves, neighbour, flow + cflow * cost, time_left - cost)
if not (open_valves & (1 << current)) and time_left > 0 and cnode.flow > 0:
check(open_valves | 1 << current, current, flow + cflow, time_left - 1)
return best
print(recurse())
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