1 files changed, 112 insertions, 0 deletions
diff --git a/src/21/solve.py b/src/21/solve.py
new file mode 100644
index 0000000..e2b8fce
--- /dev/null
+++ b/src/21/solve.py
@@ -0,0 +1,112 @@
+import sys
+sys.path.append("../common")
+import aoc
+from math import sqrt
+
+def parse_command(l):
+    s = l.split(" ")
+    args = [s[0]]
+    args = args + [int(v) for v in s[1:]]
+    return args
+
+data = aoc.data.split("\n")
+
+inspaddr = int(data[0][4:])
+instructs = [parse_command(l) for l in data[1:] if len(l) != 0]
+
+register = [0 for x in range(inspaddr+1)]
+
+opmap = dict()
+opmap["addr"] = lambda a, b : register[a] + register[b]
+opmap["addi"] = lambda a, b : register[a] + b
+opmap["mulr"] = lambda a, b : register[a] * register[b]
+opmap["muli"] = lambda a, b : register[a] * b
+opmap["banr"] = lambda a, b : register[a] & register[b]
+opmap["bani"] = lambda a, b : register[a] & b
+opmap["borr"] = lambda a, b : register[a] | register[b]
+opmap["bori"] = lambda a, b : register[a] | b
+opmap["setr"] = lambda a, b : register[a]
+opmap["seti"] = lambda a, b : a
+opmap["gtir"] = lambda a, b : 1 * (a > register[b])
+opmap["gtri"] = lambda a, b : 1 * (register[a] > b)
+opmap["gtrr"] = lambda a, b : 1 * (register[a] > register[b])
+opmap["eqir"] = lambda a, b : 1 * (a == register[b])
+opmap["eqri"] = lambda a, b : 1 * (register[a] == b)
+opmap["eqrr"] = lambda a, b : 1 * (register[a] == register[b])
+
+def varname(v):
+    return "R"+str(v)
+
+dismap = dict()
+dismap["addr"] = lambda a, b : "%s + %s" % (varname(a), varname(b))
+dismap["addi"] = lambda a, b : "%s + %d" % (varname(a), b)
+dismap["mulr"] = lambda a, b : "%s * %s" % (varname(a), varname(b))
+dismap["muli"] = lambda a, b : "%s * %d" % (varname(a), b)
+dismap["banr"] = lambda a, b : "%s & %s" % (varname(a), varname(b))
+dismap["bani"] = lambda a, b : "%s & %d" % (varname(a), b)
+dismap["borr"] = lambda a, b : "%s | %s" % (varname(a), varname(b))
+dismap["bori"] = lambda a, b : "%s | %d" % (varname(a), b)
+dismap["setr"] = lambda a, b : "%s" % (varname(a))
+dismap["seti"] = lambda a, b : "%d" % (a)
+dismap["gtir"] = lambda a, b : "(%d > %s)" % (a, varname(b))
+dismap["gtri"] = lambda a, b : "(%s > %d)" % (varname(a), b)
+dismap["gtrr"] = lambda a, b : "(%s > %s)" % (varname(a), varname(b))
+dismap["eqir"] = lambda a, b : "(%d == %s)" % (a, varname(b))
+dismap["eqri"] = lambda a, b : "(%s == %d)" % (varname(a), b)
+dismap["eqrr"] = lambda a, b : "(%s == %s)" % (varname(a), varname(b))
+
+def disassemble(s, e):
+    for i in range(s, e):
+        ins = instructs[i]
+        aoc.debug(i ,":",varname(ins[3]),"=", dismap[ins[0]](ins[1], ins[2]))
+    aoc.debug()
+
+def execute():
+    global register, insptr
+
+    while register[inspaddr] < len(instructs):
+        insptr = register[inspaddr]
+        ins = instructs[insptr]
+
+        # execute command
+        if len(register) <= ins[3]:
+            register += [0 for x in range(ins[3] - len(register) + 1)]
+        register[ins[3]] = opmap[ins[0]](ins[1], ins[2])
+
+        # part 1
+        #if insptr == 13 and register[4] == 1:
+        #    aoc.debug(register)
+        #    return
+
+        # increment instruction pointer
+        register[inspaddr] += 1
+
+def solve1(args):
+    r0 = 1797184 # (first opportunity for comparison r1 and r0)
+
+    #disassemble(0, len(instructs))
+    #execute()
+
+    return r0
+
+def solve2(args):
+    r1 = 0
+    candidates = list()
+    while True:
+        r4 = r1 | 65536 # flip 9th bit
+        r1 = 3798839
+        while True: # scan bytes of r4 and add them to r1 and multiply
+            r5 = r4 & 255
+            r1 += r5
+            r1 = r1 & 16777215
+            r1 *= 65899  # equals 1 00000001 01101011
+            r1 = r1 & 16777215
+            if r4 < 256:
+                break
+            r4 = int(r4/256) # bit shift 8 to the right
+        if r1 not in candidates:
+            candidates.append(r1)
+        elif r1 == candidates[-1]:
+            return candidates[-1]
+
+aoc.run(solve1, solve2, sols=[1797184, 11011493])