Solve 2016 days 12 and 13.

2016/d12.py

@@ -0,0 +1,43 @@
+from lib import *
+
+data = open(0).read().strip()
+part_2 = True
+
+REGS = "abcd"
+
+regs = {c: 0 for c in REGS}
+
+if part_2:
+    regs["c"] = 1
+
+insts = data.splitlines()
+
+i = 0
+while i < len(insts):
+    parts = insts[i].split()
+
+    cmd = parts[0]
+    if cmd == "cpy":
+        if parts[1] in "abcd":
+            regs[parts[2]] = regs[parts[1]]
+        else:
+            regs[parts[2]] = int(parts[1])
+    elif cmd == "jnz":
+        val = 0
+        if parts[1] in "abcd":
+            val = regs[parts[1]]
+        else:
+            val = int(parts[1])
+        if val != 0:
+            i += int(parts[2])
+            continue
+    elif cmd == "inc":
+        regs[parts[1]] += 1
+    elif cmd == "dec":
+        regs[parts[1]] -= 1
+    else:
+        assert False
+    i += 1
+
+
+print(regs["a"])

2016/d13.py

@@ -0,0 +1,36 @@
+import sys
+from lib import *
+
+data = int(open(0).read().strip())
+part2 = True
+
+def is_wall(x, y):
+    v = x*x + 3*x + 2*x*y + y + y*y
+    v += data
+    bin_count = bin(v).count("1")
+    if bin_count % 2 == 0:
+        return False
+    return True
+
+
+seen = set()
+poss = [(1, 1)]
+
+
+for step in range(51):
+    nposs = []
+    for pos in poss:
+        if pos in seen:
+            continue
+        seen.add(pos)
+        if not part2 and pos == (31, 39):
+            print(step)
+            sys.exit(0)
+        for (x, y) in [(-1, 0), (1, 0), (0, 1), (0, -1)]:
+            nx, ny = pos[0] + x, pos[1] + y
+            if nx >= 0 and ny >= 0 and not is_wall(nx, ny):
+                nposs.append((nx, ny))
+    poss = nposs
+
+if part2:
+    print(len(seen))

README.md

@@ -44,4 +44,6 @@ written in Python.
 - Day 9: 26:00 okay
 - Day 10: 23:07 okay
 - Day 11: 75:00 -__-
-- Day 12:
+- Day 12: 10:05 okay
+- Day 13: 9:43 okayish
+- Day 14: