finish 2023

2023/go/day16/day16.py

@@ -0,0 +1,68 @@
+#!/usr/bin/python3
+import sys
+import re
+from copy import deepcopy
+from math import gcd
+from collections import defaultdict, Counter, deque
+D = open(sys.argv[1]).read().strip()
+L = D.split('\n')
+G = [[c for c in row] for row in L]
+
+R = len(G)
+C = len(G[0])
+
+DR = [-1, 0, 1, 0]
+DC = [ 0, 1, 0,-1]
+
+def step(r,c,d):
+  return (r+DR[d], c+DC[d], d)
+
+def score(sr,sc,sd):
+  POS = [(sr,sc,sd)]
+  SEEN = set()
+  SEEN2 = set()
+  while True:
+    NP = []
+    if not POS:
+      break
+    for (r,c,d) in POS:
+      #print(r,c,d)
+      if 0<=r<R and 0<=c<C:
+        SEEN.add((r,c))
+        if (r,c,d) in SEEN2:
+          continue
+        SEEN2.add((r,c,d))
+        ch = G[r][c]
+        if ch=='.':
+          NP.append(step(r,c,d))
+        elif ch=='/':
+          # up right down left
+          NP.append(step(r,c,{0:1, 1:0, 2:3, 3:2}[d]))
+        elif ch=='\\':
+          NP.append(step(r,c,{0:3, 1:2, 2:1, 3:0}[d]))
+        elif ch=='|':
+          if d in [0,2]:
+            NP.append(step(r,c,d))
+          else:
+            NP.append(step(r, c, 0))
+            NP.append(step(r, c, 2))
+        elif ch=='-':
+          if d in [1,3]:
+            NP.append(step(r,c,d))
+          else:
+            NP.append(step(r, c, 1))
+            NP.append(step(r, c, 3))
+        else:
+          assert False
+    POS = NP
+  return len(SEEN)
+
+print(score(0,0,1))
+ans = 0
+for r in range(R):
+  ans = max(ans, score(r,0,1))
+  ans = max(ans, score(r,C-1,3))
+for c in range(C):
+  ans = max(ans, score(0,c,2))
+  ans = max(ans, score(R-1,c,0))
+print(ans)