Solve 2015 days 8-10.

2015/d10.py

@@ -0,0 +1,35 @@
+from functools import lru_cache
+data = open(0).read().strip()
+
+part_1 = False
+if part_1:
+    repeats = 40
+else:
+    repeats = 50
+
+@lru_cache
+def look_and_say(data: str) -> str:
+    r = ""
+    i = 0
+    while i < len(data):
+        count = 0
+        c = data[i]
+        while i < len(data) and data[i] == c:
+            count += 1
+            i += 1
+        r += f"{count}{c}"
+    return r
+
+CHUNK_SIZE = 10000
+for _ in range(repeats):
+    ndata = ""
+    lo, up = 0, CHUNK_SIZE
+    while up < len(data):
+        while up < len(data) and data[up - 1] == data[up]:
+            up += 1
+        ndata += look_and_say(data[lo:up])
+        lo, up = up, up + CHUNK_SIZE
+    ndata += look_and_say(data[lo:up])
+    data = ndata
+
+print(len(data))

2015/d8.py

@@ -0,0 +1,26 @@
+from lib import *
+
+data = open(0).read()
+part_1 = False
+
+if part_1:
+    r1 = re.compile(r"\\x[0-9a-f][0-9a-f]")
+    r2 = re.compile(r"\\\\")
+    r3 = re.compile(r"\\\"")
+
+    enc, mem = 0, 0
+    for line in data.splitlines():
+        mem += len(line)
+        line = r1.sub("^", line)
+        line = r2.sub("^", line)
+        line = r3.sub("^", line)
+        enc += len(line) - 2
+    print(mem - enc)
+else:
+    ori, enc = 0, 0
+    for line in data.splitlines():
+        ori += len(line)
+        line = line.replace("\\", "\\\\")
+        line = line.replace("\"", "\\\"")
+        enc += len(line) + 2
+    print(enc - ori)

2015/d9.py

@@ -0,0 +1,42 @@
+from lib import *
+from typing import Iterator
+
+# Just for fun instead of using itertools.permutations.
+def permutations(xs) -> Iterator:
+    assert len(xs) > 0
+    if len(xs) == 1:
+        yield xs
+    else:
+        x = xs.pop()
+        for p in permutations(xs):
+            for i in range(len(p) + 1):
+                pn = list(p)
+                pn.insert(i, x)
+                yield pn
+
+part_1 = False
+data = open(0).read()
+
+dists = {}
+nodes = set()
+for line in data.splitlines():
+    path, dist = line.split(" = ")
+    dist = int(dist)
+    a, b = path.split(" to ")
+    nodes.add(a)
+    nodes.add(b)
+    dists[(a, b)] = dist
+    dists[(b, a)] = dist
+
+if part_1:
+    mdist = 10**12
+    for route in permutations(nodes):
+        dist = sum([dists[(route[i], route[i + 1])] for i in range(len(route) - 1)])
+        mdist = min(dist, mdist)
+    print(mdist)
+else:
+    mdist = 0
+    for route in permutations(nodes):
+        dist = sum([dists[(route[i], route[i + 1])] for i in range(len(route) - 1)])
+        mdist = max(dist, mdist)
+    print(mdist)