Solve 2021 day 12-14

2021/d12.py

@@ -0,0 +1,56 @@
+from lib import get_data
+from lib import Grid2D
+from lib import ints
+from collections import deque
+from collections import defaultdict
+
+data = get_data(__file__).strip()
+g = defaultdict(list)
+
+
+for line in data.splitlines():
+    a, b = line.strip().split("-")
+    g[a].append(b)
+    g[b].append(a)
+
+
+def no_doubles(path):
+    path = [p for p in path if p.islower()]
+    return len(path) == len(set(path))
+
+
+for part in [1, 2]:
+    start = ("start", ())
+    visited = set()
+    queue = deque([start])
+
+    total = 0
+    while queue:
+        vertex = queue.popleft()
+        if vertex in visited:
+            continue
+        visited.add(vertex)
+
+        current, path = vertex
+
+        neighbors = []
+        for neighbor in g[current]:
+            if neighbor == "end":
+                total += 1
+            elif neighbor == "start":
+                continue
+            elif neighbor.islower():
+                if neighbor not in path or (part == 2 and no_doubles(path)):
+                    new_path = tuple(list(path) + [neighbor])
+                    nb = (neighbor, new_path)
+                    if nb not in visited:
+                        queue.append(nb)
+            elif neighbor.isupper():
+                new_path = tuple(list(path) + [neighbor])
+                nb = (neighbor, new_path)
+                if nb not in visited:
+                    queue.append(nb)
+            else:
+                assert False
+
+    print(total)

2021/d13.py

@@ -0,0 +1,51 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__).strip()
+
+
+def print_from_xy(xs):
+    x_min = min(v[0] for v in xs)
+    x_max = max(v[0] for v in xs)
+    y_min = min(v[1] for v in xs)
+    y_max = max(v[1] for v in xs)
+    for y in range(y_min, y_max + 1):
+        row = ""
+        for x in range(x_min, x_max + 1):
+            if (x, y) in xs:
+                row += "#"
+            else:
+                row += " "
+        print(row)
+
+
+p1, p2 = data.split("\n\n")
+xs = set([tuple(ints(line)) for line in p1.splitlines()])
+
+folds = []
+for line in p2.splitlines():
+    d = "x" if "x=" in line else "y"
+    (n,) = ints(line)
+    folds.append((d, n))
+
+
+first = None
+for d, n in folds:
+    if d == "x":
+        to_move = [(x, y) for (x, y) in xs if x > n]
+        for x, y in to_move:
+            xs.remove((x, y))
+            new_x = n - (x - n)
+            xs.add((new_x, y))
+    elif d == "y":
+        to_move = [(x, y) for (x, y) in xs if y > n]
+        for x, y in to_move:
+            xs.remove((x, y))
+            new_y = n - (y - n)
+            xs.add((x, new_y))
+    else:
+        assert False
+    first = first or len(xs)
+
+print(first)
+print_from_xy(xs)

2021/d14.py

@@ -0,0 +1,43 @@
+from lib import get_data
+from itertools import pairwise
+from collections import defaultdict
+
+data = get_data(__file__)
+orig_t, p2 = data.split("\n\n")
+
+pairs = {}
+for line in p2.splitlines():
+    ls, rs = line.split(" -> ")
+    assert ls not in pairs
+    pairs[ls] = rs
+
+for steps in [10, 40]:
+    t = str(orig_t)
+    start_letter = t[0]
+    end_letter = t[-1]
+    td = defaultdict(int)
+    for a, b in pairwise(t):
+        td[a + b] += 1
+
+    for _ in range(steps):
+        ntd = defaultdict(int)
+        for pair, count in td.items():
+            if pair in pairs:
+                a, b = pair
+                c = pairs[pair]
+                ntd[a + c] += count
+                ntd[c + b] += count
+            else:
+                ntd[pair] += count
+        td = ntd
+
+    counts = defaultdict(int)
+    for (a, b), count in td.items():
+        counts[a] += count
+        counts[b] += count
+    counts = {k: v // 2 for k, v in counts.items()}
+    counts[start_letter] += 1
+    counts[end_letter] += 1
+
+    r = max(counts.values()) - min(counts.values())
+    print(r)