[Python/2016] Move solutions into .py files

Python/2016/21.py

@@ -0,0 +1,61 @@
+from lib import *
+
+input = read_input(2016, 21)
+
+import re
+
+
+def scramble(inp):
+    (*out,) = inp
+
+    for line in input.splitlines():
+        if match := re.match(r"^swap position (\d+) with position (\d+)$", line):
+            x, y = map(int, match.groups())
+
+            out[x], out[y] = out[y], out[x]
+
+        if match := re.match(r"^swap letter ([a-zA-Z\d]+) with letter ([a-zA-Z\d]+)$", line):
+            x, y = match.groups()
+
+            out = [[[c, x][c == y], y][c == x] for c in out]
+
+        if match := re.match(r"^rotate (left|right) (\d+) steps?$", line):
+            d, n = match.groups()
+
+            n = int(n)
+
+            if d == "right":
+                n *= -1
+
+            n %= len(out)
+
+            out = out[n:] + out[:n]
+
+        if match := re.match(r"^rotate based on position of letter ([a-zA-Z\d]+)$", line):
+            (x,) = match.groups()
+
+            idx = out.index(x)
+
+            n = -(1 + idx + (idx >= 4)) % len(out)
+
+            out = out[n:] + out[:n]
+
+        if match := re.match(r"^reverse positions (\d+) through (\d+)$", line):
+            x, y = sorted(map(int, match.groups()))
+
+            out = out[:x] + out[x : y + 1][::-1] + out[y + 1 :]
+
+        if match := re.match(r"^move position (\d+) to position (\d+)$", line):
+            x, y = map(int, match.groups())
+
+            out.insert(y, out.pop(x))
+
+    return "".join(out)
+
+
+print(scramble("abcdefgh"))
+
+for it in itertools.permutations("abcdefgh"):
+    if scramble(inp := "".join(it)) == "fbgdceah":
+        print(inp)
+        break