Solve 2019 day 21

2019/21_springdroid.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+import sys
+from intcode import read_program, run
+
+def run_springscript(program, script):
+    inputs = list(map(ord, reversed(script)))
+    interp = run(program, inputs.pop, 1000)
+    return next(out for out in interp if out > 128)
+
+# Jump if A or C is a hole and D is reachable:
+# J = (!A | !C) & D
+walkscript = '''
+NOT A T
+NOT C J
+OR T J
+AND D J
+WALK
+'''.lstrip()
+
+# Jump if A is a hole, or B/C are holes and D is reachable, but we don't end up
+# just before a hole at which we will have to jump but cannot:
+# J = !A | (D & (!B | !C) & !(!E & !H))
+#   = (!(B & C) & (E | H) & D) | !A
+runscript = '''
+OR B T
+AND C T
+NOT T J
+NOT E T
+NOT T T
+OR H T
+AND T J
+AND D J
+NOT A T
+OR T J
+RUN
+'''.lstrip()
+
+program = read_program(sys.stdin)
+print(run_springscript(program, walkscript))
+print(run_springscript(program, runscript))