Solve 2025 day 9 pt 2

Flood fill was too expensive, so I tried solving it with ray casting.

I believe it is the 2nd or 3rd time during 11 runs where it has been
requested.

wip

wip

2025-python/README.md

@@ -0,0 +1,45 @@
+# Advent of Code 2025
+
+Solutions for #aoc2025 in Python 3 (3.13.4).
+
+Programming setup:
+
+- Lenovo Thinkpad T14
+- OpenSUSE Tumbleweed with labwc
+- Helix editor w/ Ruff LS
+- Vivaldi
+- Foot
+
+## Help scripts
+
+Display all solved puzzles:
+
+    python aoc.py
+
+To bootstrap a new puzzle (creates `input/<day_no>.txt` and `output/day_<day_no>.py`):
+
+    python aoc.py <day_no> new
+
+Manually copy the puzzle input from https://adventofcode.com and paste it in `input/<day_no>.txt`
+to start coding.
+
+    wl-paste > input/<day_no>.txt
+
+Solve separate puzzle (replace `XX` with the puzzle number):
+
+    python -m output.day_XX
+
+Solve separate puzzle using stdin (replace `XX` with the puzzle number):
+
+    wl-paste | python -m output.day_XX
+    cat tmpfile | python -m output.day_XX
+
+Execute separate puzzle on file save (replace `XX` with the puzzle number):
+
+    ls output/*.py | entr -c -s 'wlpaste | python -m output.day_XX'
+    ls output/*.py | entr -c -s 'cat tmpfile | python -m output.day_XX'
+    ls output/*.py | entr -c -r python -m output.day_XX
+
+(requires `entr` and `wl-paste`, Mac users can instead use `pbpaste`. If you
+prefer X at Linux, use `xclip -selection clipboard -o`).
+

2025-python/aoc.py

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+import sys
+from pathlib import Path
+
+
+def headline(n):
+    """Print day number and name, followed by a ruler. Used by the answer decorator"""
+    print(f"\nDay {int(n)} - https://adventofcode.com/{year}/day/{int(n)}\n")
+
+
+year = 2025
+nostrip = []
+
+try:
+    _, day_no, *name = sys.argv
+except ValueError:
+    day_no = None
+    name = None
+
+Path("./input").mkdir(parents=True, exist_ok=True)
+Path("./output").mkdir(parents=True, exist_ok=True)
+
+if day_no and name:
+    name = " ".join(name)
+    padded_no = day_no.zfill(2)
+    with open("output/day_{}.py".format(padded_no), "w") as s:
+        s.write(
+            f"""
+import re
+from collections import deque, Counter, defaultdict
+from heapq import heappop, heappush
+from itertools import compress, combinations, chain, permutations
+
+from output import matrix, D, DD, ADJ, ints, sints, mhd, mdbg, vdbg, cw, ccw, bk
+
+
+def solve(data):
+    p1 = None
+    p2 = None
+    return p1, p2
+
+
+if __name__ == "__main__":
+    import os
+
+    # use dummy data
+    inp = \"\"\"
+        replace me
+    \"\"\".strip()
+
+    # uncomment to instead use stdin
+    # import sys; inp = sys.stdin.read().strip()
+
+    # uncomment to use AoC provided puzzle input
+    # with open("./input/{padded_no}.txt", "r") as f:
+    #     inp = f.read().strip()
+
+    # uncomment to do initial data processing shared by part 1-2
+    p1, p2 = solve(inp)
+
+    print(p1)
+    os.system(f"echo {{p1}} | wl-copy")
+    # print(p2)
+    # os.system(f"echo {{p2}} | wl-copy")
+
+    # uncomment and replace 0 with actual output to refactor code
+    # and ensure nonbreaking changes
+    # assert p1 == 0
+    # assert p2 == 0
+""".strip()
+            + "\n"
+        )
+    exit(0)
+
+print(
+    f"\n\033[95m\033[1mAdvent of Code {year}\033[0m"
+    "\n###################"
+    "\n\n\033[96mby Anders Englöf Ytterström\033[0m"
+)
+
+
+stars = 0
+for i in [str(n).zfill(2) for n in range(1, 26)]:
+    if not day_no or day_no.zfill(2) == i:
+        try:
+            day = __import__(
+                "output.day_{}".format(i),
+                globals(),
+                locals(),
+                ["solve"],
+                0,
+            )
+            with open(f"./input/{i}.txt", "r") as f:
+                data = f.read()
+                if int(i) not in nostrip:
+                    data = data.strip()
+            headline(i)
+            try:
+                data = day.presolve(data)
+            except AttributeError:
+                pass
+            try:
+                p1, p2 = day.solve(data)
+            except AttributeError:
+                pass
+            if p1:
+                print(f"    \033[92m1)\033[0m {p1}")
+                stars += 1
+            if p2:
+                print(f"    \033[92m2)\033[0m {p2}")
+                stars += 1
+        except IOError:
+            pass
+        except ImportError:
+            pass
+if not day_no:
+    print(f"\nStars: {stars}")
+    print("".join("*" if n < stars else "•" for n in range(24)))
+print("")

2025-python/output/__init__.py

@@ -0,0 +1,257 @@
+import re
+from math import inf
+from PIL import Image
+
+# Directions/Adjacents for 2D matrices, in the order UP, RIGHT, DOWN, LEFT
+D = [
+    (-1, 0),
+    (0, 1),
+    (1, 0),
+    (0, -1),
+]
+
+Di = [
+    (-1, -1),
+    (-1, 1),
+    (1, -1),
+    (1, 1),
+]
+
+# Directions for 2D matrices, as a dict with keys U, R, D, L
+DD = {
+    "U": (-1, 0),
+    "R": (0, 1),
+    "D": (1, 0),
+    "L": (0, -1),
+}
+
+DDa = {
+    "^": (-1, 0),
+    ">": (0, 1),
+    "v": (1, 0),
+    "<": (0, -1),
+}
+
+# Adjacent relative positions including diagonals for 2D matrices, in the order NW, N, NE, W, E, SW, S, SE
+ADJ = [
+    (-1, -1),
+    (-1, 0),
+    (-1, 1),
+    (0, -1),
+    (0, 1),
+    (1, 1),
+    (1, 0),
+    (1, -1),
+]
+
+
+def ints(s):
+    """Extract all integers from a string"""
+    return [int(n) for n in re.findall(r"\d+", s)]
+
+
+def sints(s):
+    """Extract all signed integers from a string"""
+    return [int(n) for n in re.findall(r"-?\d+", s)]
+
+
+def mhd(a, b):
+    """Calculates the Manhattan distance between 2 positions in the format (y, x) or (x, y)"""
+    ar, ac = a
+    br, bc = b
+    return abs(ar - br) + abs(ac - bc)
+
+
+def grid(d, o="#"):
+    """Transform a string into an iterable matrix. Returns the matrix, row count and col count"""
+    m = [tuple(r) for r in d.split()]
+    return set([(r, c) for c in range(len(m[0])) for r in range(len(m)) if m[r][c] == o])
+
+
+def matrix(d):
+    """Transform a string into an iterable matrix. Returns the matrix, row count and col count"""
+    m = [tuple(r) for r in d.split()]
+    return m, len(m), len(m[0])
+
+
+def mdbg(m):
+    """Print-debug a matrix"""
+    for r in m:
+        print("".join(r))
+
+
+def vdbg(seen, mask=("#", "."), M=None):
+    """Print-debug visited positions of a matrix"""
+    t = inf
+    l = inf
+    b = 0
+    r = 0
+    for y, x in seen:
+        t = min(t, y)
+        r = max(r, x)
+        b = max(b, y)
+        l = min(l, x)
+    H = b + 1
+    W = r + 1
+    osr = 0 #t
+    osc = 0 #l
+    C, Z = mask
+    def _m(r, c):
+        return M[r][c] if M else Z
+    O = []
+    for r in range(H):
+        O.append("".join([C if (r + osr, c + osc) in seen else _m(r, c) for c in range(W)]))
+    print("\n".join(O))
+
+
+def svg(seen):
+    """Print-debug visited positions of a matrix"""
+    t = inf
+    l = inf
+    b = 0
+    r = 0
+    rects = []
+    for y, x in seen:
+        t = min(t, y)
+        r = max(r, x)
+        b = max(b, y)
+        l = min(l, x)
+    H = b - t + 1
+    W = r - l + 1
+    print(t, r, b, l)
+    im = Image.new(mode="RGB", size=(W,H), color=(255,255,255))
+    for y, x in seen:
+        im.putpixel((x-l, y-t), (0, 0, 0, 255))
+    im.save("aoc.png")
+    
+    for y, x in seen:
+        rects.append(f"<rect x='{x-l}' y='{y-t}' width='1' fill='black' stroke='black' stroke-width='10' height='1' />")
+    with open("svg.svg", "w") as f:
+        f.write(f"""
+                <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 {W} {H}" width="{W}" height="{H}">
+                    {"".join(rects)}
+                </svg>    
+                """.strip())
+
+
+def vvdbg(seen, h, w):
+    """Print-debug visited positions of a matrix, with values"""
+    for r in range(h):
+        print("".join([seen[(r, c)] if (r, c) in seen else "." for c in range(w)]))
+
+
+def cw(y, x):
+    """Flip a (y, x) direction counterwise: U->R, R->D, D->L, L->U.
+
+    >>> cw(-1, 0)
+    (0, 1)
+    >>> cw(0, 1)
+    (1, 0)
+    >>> cw(1, 0)
+    (0, -1)
+    >>> cw(0, -1)
+    (-1, 0)
+    """
+    return (x, y) if y == 0 else (x, -y)
+
+
+def ccw(y, x):
+    """Flip a (y, x) direction counterwise: U->L, L->D, D->R, R->U.
+
+    >>> ccw(-1, 0)
+    (0, -1)
+    >>> ccw(0, -1)
+    (1, 0)
+    >>> ccw(1, 0)
+    (0, 1)
+    >>> ccw(0, 1)
+    (-1, 0)
+    """
+    return (x, y) if x == 0 else (-x, y)
+
+
+def bfs(S, E=None):
+    """BFS algorithm, equal weighted nodes"""
+    seen = set()
+    q = [(S, 0)]
+    g = {}  # graph, required to be provided at some point
+    while q:
+        m, w = q.pop(0)
+        if m in seen:
+            continue
+        seen.add(m)
+        # investigate here
+        for s in g[m]:
+            q.append((s, w + 1))
+    # return insights
+
+
+def mhd_search(r, c, R=20):
+    """returns all coords that are within R manhattan distance from (r,c)"""
+    p = set()
+    for d in range(1, R + 1):
+        p.add((r, c + d))
+        p.add((r, c - d))
+        p.add((r + d, c))
+        p.add((r - d, c))
+        for dd in range(d):
+            p.add((r - dd, c - d + dd))
+            p.add((r + dd, c - d + dd))
+            p.add((r - dd, c - dd + d))
+            p.add((r + dd, c - dd + d))
+    return p
+
+
+def dijkstras(grid, start, target):
+    """
+    1. Create an array that holds the distance of each vertex from the starting
+       vertex. Initially, set this distance to infinity for all vertices except
+       the starting vertex which should be set to 0.
+    2. Create a priority queue (heap) and insert the starting vertex with its
+       distance of 0.
+    3. While there are still vertices left in the priority queue, select the vertex
+       with the smallest recorded distance from the starting vertex and visit its
+       neighboring vertices.
+    4. For each neighboring vertex, check if it is visited already or not. If it
+       isn’t visited yet, calculate its tentative distance by adding its weight
+       to the smallest distance found so far for its parent/previous node
+       (starting vertex in case of first-level vertices).
+    5. If this tentative distance is smaller than previously recorded value
+       (if any), update it in our ‘distances’ array.
+    6. Finally, add this visited vertex with its updated distance to our priority
+       queue and repeat step-3 until we have reached our destination or exhausted
+       all nodes.
+    """
+    import heapq
+
+    target = max(grid)
+    seen = set()
+    queue = [(start, 0)]
+    while queue:
+        cost, pos, direction, steps = heapq.heappop(queue)
+        y, x = pos
+        dy, dx = direction
+
+        if pos == target:
+            return cost
+
+        if ((pos, "and stuff")) in seen:
+            continue
+
+        seen.add((pos, "and stuff"))
+
+        neighbors = []
+        for n in neighbors:
+            heapq.heappush(queue, ("stuffs"))
+
+    return -1
+
+
+def bk(graph, p, r=set(), x=set()):
+    """Bron-Kerbosch algoritm, no pivot: https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm"""
+    if not p and not x:
+        yield r
+    while p:
+        v = p.pop()
+        yield from bk(graph, p & set(graph[v]), r | {v}, x & graph[v])
+        x.add(v)

2025-python/output/day_01.py

@@ -0,0 +1,29 @@
+def solve(data):
+    d = 50
+    p1 = 0
+    p2 = 0
+    for s in data.split():
+        sf0 = d == 0
+        m, T = (-1, 99) if s[0] == "L" else (1, 1)
+        for _ in range(int(s[1:])):
+            d = (d + m) % 100
+            if d == T:
+                if sf0:
+                    sf0 = False
+                    continue
+                p2 += 1
+        p1 += d == 0
+    return p1, p1 + p2
+
+
+if __name__ == "__main__":
+    with open("./input/01.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 1195
+    assert p2 == 6770

2025-python/output/day_02.py

@@ -0,0 +1,35 @@
+import re
+
+from output import ints
+
+
+def solve(data):
+    p1 = set()
+    p2 = set()
+    R = re.compile(r"^(\w+)\1+$")
+    for line in data.split(","):
+        a, b = ints(line)
+        for n in range(a, b + 1):
+            s = str(n)
+            ls = len(s)
+            for seq in re.findall(R, s):
+                sqrts = [i for i in range(1, ls + 1) if ls % i == 0]
+                for t in sqrts:
+                    if "".join([seq] * t) == s:
+                        if t == 2:
+                            p1.add(n)
+                        p2.add(n)
+    return sum(p1), sum(p2)
+
+
+if __name__ == "__main__":
+    with open("./input/02.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 38437576669
+    assert p2 == 49046150754

2025-python/output/day_03.py

@@ -0,0 +1,31 @@
+def solve(data):
+    p1 = 0
+    p2 = 0
+    for line in data.splitlines():
+        p1 += _maxj(line, 2)
+        p2 += _maxj(line, 12)
+    return p1, p2
+
+
+def _maxj(line, C):
+    toexcl = len(line) - C
+    batt = []
+    for c in line:
+        while toexcl and batt and batt[-1] < c:
+            toexcl -= 1
+            batt.pop()
+        batt.append(c)
+    return sum(10**x * int(y) for x, y in zip(range(C - 1, -1, -1), batt))
+
+
+if __name__ == "__main__":
+    with open("./input/03.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 17430
+    assert p2 == 171975854269367

2025-python/output/day_04.py

@@ -0,0 +1,31 @@
+from output import grid, ADJ
+
+
+def solve(data):
+    p1 = 0
+    p2 = set()
+    G = grid(data, o="@")
+    while True:
+        for r, c in G:
+            if sum((r + dy, c + dx) in G for dy, dx in ADJ) < 4:
+                p2.add((r, c))
+        if p1 == 0:
+            p1 = len(p2)
+        if not G & p2:
+            break
+        G = G - p2
+    p2 = len(p2)
+    return p1, p2
+
+
+if __name__ == "__main__":
+    with open("./input/04.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 1493
+    assert p2 == 9194

2025-python/output/day_05.py

@@ -0,0 +1,31 @@
+from output import ints
+
+
+def solve(data):
+    p1 = None
+    p2 = 0
+    ranges, ids = data.split("\n\n")
+    ids = ints(ids)
+    R = [ints(line) for line in ranges.split()]
+    p1 = sum(any(s <= n <= e for s, e in R) for n in ids)
+    c = 0
+    for s, e in sorted(R):
+        s = max(c + 1, s)
+        if s <= e:
+            p2 += e - s + 1
+            c = max(e, c)
+
+    return p1, p2
+
+
+if __name__ == "__main__":
+    with open("./input/05.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 509
+    assert p2 == 336790092076620

2025-python/output/day_06.py

@@ -0,0 +1,40 @@
+import re
+from math import prod
+
+
+def solve(data):
+    p1 = 0
+    p2 = 0
+    rows = data.splitlines()
+    J = max(len(r) for r in rows) + 1
+    rows = [r.ljust(J) for r in rows]
+    ops = rows.pop()
+    s = 0
+    for ows in re.findall(r"(\S\s+)", ops):
+        o, *ws = ows
+        e = s + len(ws)
+        col = [ns for ns in [r[s:e] for r in rows]]
+        s += len(ows)
+        col1 = [int(r) for r in col]
+        col2 = [int("".join([nsc for nsc in ns if nsc.isdigit()])) for ns in zip(*col)]
+        match o:
+            case "*":
+                p1 += prod(col1)
+                p2 += prod(col2)
+            case "+":
+                p1 += sum(col1)
+                p2 += sum(col2)
+    return p1, p2
+
+
+if __name__ == "__main__":
+    with open("./input/06.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 5524274308182
+    assert p2 == 8843673199391

2025-python/output/day_07.py

@@ -0,0 +1,50 @@
+import functools
+from output import grid
+
+
+def solve(data):
+    G = grid(data, o="^")
+    p1 = set()
+    p2 = 0
+    H = len(data.split())
+    W = len(data.split()[0])
+    S = (0, data.split()[0].index("S"))
+    Q = [S]
+    while Q:
+        y, x = Q.pop(0)
+        if y == H:
+            continue
+        if (y, x) in p1:
+            continue
+        if (y, x) in G:
+            Q.append((y, x - 1))
+            Q.append((y, x + 1))
+            p1.add((y, x))
+        else:
+            Q.append((y + 1, x))
+    p1 = len(p1)
+
+    @functools.cache
+    def _timelines(p):
+        y, x = p
+        if not 0 <= y < H or not 0 <= x < W:
+            return 1
+        if p in G:
+            return _timelines((y, x - 1)) + _timelines((y, x + 1))
+        return _timelines((y + 1, x))
+
+    p2 = _timelines(S)
+    return p1, p2
+
+
+if __name__ == "__main__":
+    with open("./input/07.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 1539
+    assert p2 == 6479180385864

2025-python/output/day_08.py

@@ -0,0 +1,58 @@
+from math import sqrt
+from itertools import combinations
+
+from output import ints
+
+
+def solve(data):
+    Di = sorted(
+        map(_euclidan_distance, combinations(data.splitlines(), r=2)),
+        key=lambda r: r[1],
+    )
+    C = []
+    S = len(data.splitlines())
+    IP = 1000
+    for i, pq in enumerate(Di, start=1):
+        pq, _ = pq
+        c = set(pq)
+        p, q = pq
+        rmq = []
+        nothing = False
+        for j in C:
+            if p in j and q in j:
+                nothing = True
+                continue
+            if p in j or q in j:
+                c = c | j
+                rmq.append(j)
+        C = [e for e in C if e not in rmq]
+        if c == pq and nothing:
+            continue
+        if len(c) == S:
+            p2 = ints(p)[0] * ints(q)[0]
+            break
+        C = [c] + C
+        if i == IP:
+            a, b, c = sorted(list(map(len, C)), reverse=True)[:3]
+            p1 = a * b * c
+    return p1, p2
+
+
+def _euclidan_distance(pq):
+    p, q = pq
+    p1, p2, p3 = ints(p)
+    q1, q2, q3 = ints(q)
+    return (p, q), sqrt((p1 - q1) ** 2 + (p2 - q2) ** 2 + (p3 - q3) ** 2)
+
+
+if __name__ == "__main__":
+    with open("./input/08.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 84968
+    assert p2 == 8663467782

2025-python/output/day_09.py

@@ -0,0 +1,84 @@
+from math import inf
+from itertools import combinations
+
+from output import ints
+
+
+def solve(data):
+    p1 = 0
+    p2 = 0
+    A = [tuple(ints(pos)) for pos in data.splitlines()]
+    T = inf
+    R = 0
+    B = 0
+    L = inf
+    for r, c in A:
+        T = min(r, T)
+        R = max(c, R)
+        B = max(r, B)
+        L = min(c, L)
+    S = A[0]
+    V = set()
+    W = set()
+    while True:
+        V.add(S)
+        W.add(S)
+        y, x = S
+        he = [(r, c) for r, c in A if r == y and (r, c) not in V]
+        ve = [(r, c) for r, c in A if c == x and (r, c) not in V]
+        if not he and not ve:
+            E = A[0]
+        elif he and ve:
+            E = min(min(he), min(ve))
+        elif he and not ve:
+            E = min(he)
+        else:
+            E = min(ve)
+        y2, x2 = E
+        for r in range(min(y, y2), max(y, y2) + 1):
+            for c in range(min(x, x2), max(x, x2) + 1):
+                W.add((r, c))
+        if E == A[0]:
+            break
+        S = E
+    V = V | W
+    for a, b in combinations(A, r=2):
+        y1, x1 = a
+        y2, x2 = b
+        x = abs(x1 - x2) + 1
+        y = abs(y1 - y2) + 1
+        p1 = max(p1, x * y)
+        if _within(W, a, b, T, R, B, L):
+            p2 = max(p2, max(p2, x * y))
+    return p1, p2
+
+
+def _within(W, a, b, T, R, B, L):
+    y1, x1 = a
+    y2, x2 = b
+    for r in range(min(y1, y2) + 1, max(y1, y2)):
+        for c in range(min(x1, x2) + 1, max(x1, x2)):
+            if (r, c) in W:
+                continue
+            for s, e in [(T, r), (r, B)]:
+                z = sum((nr, c) in W for nr in range(s, e))
+                if z and z % 2 == 0:
+                    return False
+            for s, e in [(L, c), (c, R)]:
+                z = sum((r, nc) in W for nc in range(s, e))
+                if z and z % 2 == 0:
+                    return False
+    return True
+
+
+if __name__ == "__main__":
+    with open("./input/09.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 4749838800
+    assert p2 == 1624057680

leaderboard/Containerfile

@@ -8,7 +8,7 @@ RUN pip install waitress==3.0.2
 
 FROM reqs AS app
 RUN mkdir /app/templates
-COPY *.jinja2 /app/templates
+COPY templates/*.jinja2 /app/templates
 COPY app.py app.py
 
 ENV AOC_TOKEN=