Day 16: 10s for part 1

2019/day16.py

@@ -4,31 +4,35 @@ import math
 def main():
     with open("day16.txt", "rt") as input_file:
         inputs = [int(i) for i in input_file.read().rstrip()]
-    inputs_orig = inputs.copy()
+        # inputs = [1,2,3,4,5,6,7,8]
+        # inputs = [0,3,0,3,6,7,3,2,5,7,7,2,1,2,9,4,4,0,6,3,4,9,1,5,6,5,4,7,4,6,6,4]
 
-    # result = phaze2phaze(inputs)
-    # print(f"First 8 digits: {''.join(str(int(i)) for i in result[:8])}")
-
-    # Part 2
-    offset = int(''.join(str(i) for i in inputs[:7]))
-    inputs = [i for _ in range(10000) for i in inputs_orig]
+    # Part 1
     result = phaze2phaze(inputs)
-    print(f"8 digits at offset: {''.join(str(int(i)) for i in result[offset:offset + 8])}")
-
+    print(f"First 8 digits: {''.join(str(int(i)) for i in result[:8])}")
 
-def phaze2phaze(inputs):
-    p = [0, 1, 0, -1]
-    for phase_id in range(100):
+    # Part 2
+    # offset = int(''.join(str(i) for i in inputs[:7]))
+    # rev_inputs = [i for _ in range(10000) for i in reversed(inputs)]
+    # rev_offset = len(rev_inputs) - offset
+
+    # print(f"Offset: {offset}. Reversed offset: {rev_offset}")
+    # result = phaze2phaze(rev_inputs, index_limit=rev_offset)
+    # result_slice = result[rev_offset - 8:rev_offset]
+    # assert result_slice == [8,4,4,6,2,0,2,6]
+    # print(f"8 digits at offset: {''.join(str(int(i)) for i in result_slice)}")
+
+def p(index, pos):
+    return round(math.cos(((pos - index + 1) // index) * (math.pi / 2)))
+
+def phaze2phaze(inputs, rounds=100, index_limit=None):
+    """ https://www.youtube.com/watch?v=i0leFvyLEF8 """
+    for phase_id in range(rounds):
         phase_id += 1
-        print(f"Phase {phase_id}...")
         outputs = [None] * len(inputs)
-        for index in range(len(inputs)):
-            ex_f = index + 1
-            ex_p = [p[i // ex_f] for i in range(len(p) * ex_f)]
-            while len(ex_p) < len(inputs) + 1:
-                ex_p += ex_p  # yikes
-            ex_p = ex_p[1:len(inputs) + 1]
-            out = sum(a * b for a, b in zip(inputs, ex_p))
+        print(f"Phase {phase_id}... ")
+        for index in range(index_limit or len(inputs)):
+            out = sum(x * p(index + 1, pos + index) for pos, x in enumerate(inputs[index:]))
             outputs[index] = abs(math.fmod(out, 10))
         inputs = outputs
     return inputs
@@ -36,4 +40,3 @@ def phaze2phaze(inputs):
 
 if __name__ == "__main__":
     main()
-