From 4c867d0024d19ffcb57bb2dbb7d6ab10603a579f Mon Sep 17 00:00:00 2001
From: Tomasz Kramkowski <tomasz@kramkow.ski>
Date: Fri, 16 Dec 2022 16:58:00 +0000
Subject: 16 faster

---
 16.py | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/16.py b/16.py
index a8819f3..c004091 100644
--- a/16.py
+++ b/16.py
@@ -1,7 +1,7 @@
 from utils import open_day
 from functools import cache
 from dataclasses import dataclass
-from itertools import count
+from itertools import count, chain
 import re
 
 @dataclass
@@ -9,6 +9,15 @@ 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:
@@ -16,16 +25,16 @@ with open_day(16) as f:
         m = regex.match(line)
         assert(m)
         valve, flow, neighbours = m.group(1, 2, 3)
-        inp[valve] = (int(flow), neighbours.split(', '))
+        inp[intern(valve)] = (int(flow), [intern(n) for n in neighbours.split(', ')])
 
 nodes = {}
 for valve, (flow, neighbours) in inp.items():
-    if valve != 'AA' and flow == 0: continue
+    if valve != 0 and flow == 0: continue
     actual_neighbours = []
     for n in neighbours:
         prev = valve
         for cost in count(1):
-            if n == 'AA' or inp[n][0] != 0: break
+            if n == 0 or inp[n][0] != 0: break
             l, r = inp[n][1]
             nnext = r if l == prev else l
             prev = n
@@ -35,21 +44,27 @@ for valve, (flow, neighbours) in inp.items():
 
 @cache
 def sum_flow(open_valves):
-    return sum(nodes[n].flow for n in 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=frozenset(), current='AA', flow=0, time_left=30):
+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
-        new = recurse(open_valves, neighbour,
-                      flow + cflow * cost, time_left - cost)
-        best = max(best, new)
-    if current not in open_valves and time_left > 0 and cnode.flow > 0:
-        best = max(best, recurse(open_valves | {current}, current,
-                                 flow + cflow, time_left - 1))
+        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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