15

15.py

@@ -0,0 +1,35 @@
+ex=[0,3,6]
+
+def iter(start):
+  spoke=dict()
+  lastSpokeD=dict()
+  turn=0
+  nextSpeak=None
+  for i in start:
+    turn+=1
+    spoke[i]=turn
+    yield i
+    nextSpeak=0
+    
+  while True:
+    turn+=1
+    yield nextSpeak
+    lastSpoke=spoke.get(nextSpeak)
+    spoke[nextSpeak]=turn
+
+    if lastSpoke is None:
+      nextSpeak=0
+    else:
+      nextSpeak=turn-lastSpoke
+    
+    if turn%3000000==0:
+      print(f"turn {turn} of 30000000 ({100*turn/30000000.0}%)")
+
+import itertools
+print(list(itertools.islice(iter(ex), 10)))
+
+def nth(start, n):
+  return next(x for i,x in enumerate(start) if i==n-1)
+
+# print(nth(iter([0,3,6]), 30000000))
+print(nth(iter([5,1,9,18,13,8,0]), 30000000))