2016/18

y2016/p16.py

@@ -0,0 +1,25 @@
+import sys
+
+
+def op(a, trans=str.maketrans('01', '10')):
+    return a + '0' + a[::-1].translate(trans)
+
+
+def checksum(string):
+    return ''.join('01'[a == b] for a, b in zip(string[::2], string[1::2]))
+
+
+def expand(string, lim):
+    while len(string) < lim:
+        string = op(string)
+    string = string[:lim]
+
+    chk = checksum(string)
+    while len(chk) % 2 == 0:
+        chk = checksum(chk)
+    return chk
+
+
+text = sys.stdin.read().strip()
+print(expand(text, 272))
+print(expand(text, 35651584))

y2016/p17.py

@@ -0,0 +1,24 @@
+import sys
+
+import toolkit
+
+
+def advance(path, pos):
+    digest = toolkit.md5(text + path)
+    for d in [d for d, c in zip('UDLR', digest) if c in 'bcdef']:
+        path1 = path + d
+        new1 = pos + mapping[d]
+        if 0 <= new1.real <= 3 and 0 <= new1.imag <= 3:
+            yield path1, new1
+
+
+text = sys.stdin.read().strip()
+mapping = {'U': -1j, 'D': 1j, 'L': -1, 'R': 1}
+edge = {('', 0)}
+valid = []
+while edge:
+    edge = {new for old in edge for new in advance(*old)}
+    valid += [new for new in edge if new[1] == 3 + 3j]
+    edge -= set(valid)
+print(valid[0][0])
+print(len(valid[-1][0]))

y2016/p18.py

@@ -0,0 +1,15 @@
+import sys
+
+
+def march(text):
+    base = '.' + text + '.'
+    for i in range(len(text)):
+        yield '.^'[base[i:i + 3] in {'^^.', '.^^', '^..', '..^'}]
+
+
+text = sys.stdin.read().strip()
+seen = [text]
+for i in range(400_000):
+    seen.append(''.join(march(seen[-1])))
+print(''.join(seen[:40]).count('.'))
+print(''.join(seen[:400_000]).count('.'))