day17 wip

examples/aoc2024/day17/part1.jou

@@ -114,6 +114,8 @@ class Machine:
     def run(self) -> None:
         while *self->ip != -1:
             self->step()
+            self->print()
+            #getchar()
 
     # Prints machine code and registers to stdout in human-readable form.
     def print(self) -> None:
@@ -154,7 +156,7 @@ class Machine:
 
 
 def main() -> int:
-    f = fopen("sampleinput.txt", "r")
+    f = fopen("input", "r")
     assert f != NULL
 
     m = Machine{}
@@ -192,13 +194,6 @@ def main() -> int:
     # Output:      4 if A != 0: jump to 0
     m.print()
 
-    # Output: Registers: A=364 B=0 C=0
-    # Output:      0 A /= 2**1
-    # Output: -->  2 output A % 8
-    # Output:      4 if A != 0: jump to 0
-    m.step()
-    m.print()
-
     # Output: 4,6,3,5,6,3,5,2,1,0
     m.run()
     for i = 0; i < m.output_len; i++:

examples/aoc2024/day17/part2.jou

@@ -0,0 +1,31 @@
+# My input looked like this, as printed by code in part 1:
+#
+#    Registers: A=... B=0 C=0
+#         0 B = A % 8
+#         2 B ^= 1
+#         4 C = A / 2**B
+#         6 B ^= 5
+#         8 B ^= C
+#        10 A /= 2**3
+#        12 output B % 8
+#        14 if A != 0: jump to 0
+#
+# Suppose that value of A register in binary looks like ....abcdefgh, where
+# abcdefgh are the last bits. For example, if A = 420 = binary 110100100, then
+# abcdefgh = 10100100. Let's step through the code and see what it does:
+#
+#    Registers: A=...abcdefgh B=0 C=0
+#         0 B = def
+#         2 B = deF         here F denotes the opposite of f
+#         4 C = fgh if deF=000
+#               efg if deF=001
+#               def if deF=010
+#               cde if deF=011
+#               bcd if deF=100
+#               abc if deF=100
+#               ..
+#         6 B ^= 5
+#         8 B ^= C
+#        10 A /= 2**3
+#        12 output B % 8
+#        14 if A != 0: jump to 0