Do day 3 and 4 for 2025

2025/d03.py

@@ -0,0 +1,35 @@
+from lib import get_data
+
+data = get_data(__file__)
+
+
+def max_joltage(xs: str, target_len: int) -> int:
+    def dynamic(xs: str) -> dict[int, str]:
+        if len(xs) == 0:
+            return {0: ""}
+
+        rs = dynamic(xs[1:])
+        for i in range(target_len, 0, -1):
+            if not (i - 1) in rs:
+                continue
+            nv = int(xs[0] + rs[i - 1])
+            if not i in rs:
+                rs[i] = str(nv)
+            elif nv > int(rs[i]):
+                rs[i] = str(nv)
+        return rs
+
+    rs = dynamic(xs)
+    return int(rs[target_len])
+
+
+r1 = 0
+r2 = 0
+for line in data.splitlines():
+    r1 += max_joltage(line, 2)
+    r2 += max_joltage(line, 12)
+
+
+print(r1)
+print(r2)
+

2025/d04.py

@@ -0,0 +1,32 @@
+from lib import get_data, Grid2D
+
+data = get_data(__file__)
+g = Grid2D(data)
+
+r = 0
+adjs = []
+for pos in g.all_coords():
+    if g[pos] != "@":
+        continue
+    nr_of_rolls_adj = len([nb for nb in g.neighbors_adj(pos) if g[nb] == "@"])
+    if nr_of_rolls_adj < 4:
+        r += 1
+        adjs.append(pos)
+print(r)
+
+r = 0
+while True:
+    adjs = []
+    for pos in g.all_coords():
+        if g[pos] != "@":
+            continue
+        nr_of_rolls_adj = len([nb for nb in g.neighbors_adj(pos) if g[nb] == "@"])
+        if nr_of_rolls_adj < 4:
+            adjs.append(pos)
+    if adjs:
+        r += len(adjs)
+        for a in adjs:
+            g[a] = "."
+    else:
+        break
+print(r)

README.md

@@ -12,7 +12,10 @@ stressful and this will actually be more fun. Thank you Eric Wastl and let's go!
   ticks naively. Maybe I should revisit this.
 - Day 2: The simple direct approach with iterating over all the IDs in the
   ranges just worked okay. Not pretty but acceptable.
-- Day 3:
+- Day 3: Fun dynamic programming problem. Part 2 took me a little too long
+  overall but it was fun.
+- Day 4: One of the easier grid based puzzles. Less than five minutes with
+  existing grid library.
 
 
 ## AoC 2024