From e6307795a499a0bb7b8e74af73cf5853cc561fe3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Anders=20Engl=C3=B6f=20Ytterstr=C3=B6m?= <yttan@fastmail.se>
Date: Sun, 15 Dec 2024 13:15:39 +0100
Subject: [PATCH] Solve 2024:14 p1-2 "Restroom Redoubt"

After working overtime to solve day 12, this brief
task was a much welcome change.

For pt 1, the code uses integer division and
modulus to update all positions. The tricky part
was to determine which quadrant got the middle
column and row (since dimensions was odd numbers,
and either left or right quandrants is +1 longer),
which was straightforward to verify by the test
cases.

For pt 2, the remains of the code used to visually
identify the tree is left under the `find_easter_egg`
toggle.

Basically, the code prints the grid with
all robots marked as a `#`, and free space as `.`.`

This wording of the puzzle is important:

> very rarely, _most of the robots_ should arrange
> themselves into a picture of a Christmas tree.

"most of the robots" means the tree will be quite
visible, which also means it is safe to asume a
significant cluster of "#" would appear over time.

By keeping track of the counter (seconds the robots
has traveled), it was evident that the cluster of `#`
occoured th first time at i=64 and every 103th
time forward.

In other words, `i % 103 == 64` will most likely
give a tree. The print statement is therefore
limited to those i's, and at `i == easter_egg_appearance`
the tree is visible.

So, to be extra clear: 64, 103 and pt2 answer is
unique to my puzzle input. If this code is used
with any other puzzle input, these numbers will
most likely vary.

For the fun, the code also contains the `display_easter_egg`
flag to actually print the tree. This is provided
to indicate how big the actual tree is: 33*36 chars.

Also, the `sints` utility function was added to
extract all signed ints from a string.
---
 2024-python/output/__init__.py |  5 ++++
 2024-python/output/day_14.py   | 55 ++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 2024-python/output/day_14.py

diff --git a/2024-python/output/__init__.py b/2024-python/output/__init__.py
index 26611f0..4ad56dc 100644
--- a/2024-python/output/__init__.py
+++ b/2024-python/output/__init__.py
@@ -42,6 +42,11 @@ def ints(s):
     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
diff --git a/2024-python/output/day_14.py b/2024-python/output/day_14.py
new file mode 100644
index 0000000..7d58cf9
--- /dev/null
+++ b/2024-python/output/day_14.py
@@ -0,0 +1,55 @@
+from output import sints, vdbg
+
+
+def solve(data, find_easter_egg=False, display_easter_egg=True):
+    W = 101
+    H = 103
+    easter_egg_recurring = 103
+    easter_egg_offset = 64
+    robots = [sints(line) for line in data.splitlines()]
+    state = {}
+    for id, robot in enumerate(robots):
+        x, y, *_ = robot
+        state[id] = (x, y)
+    i = 0
+    easter_egg_appearance = 7892
+    while i < easter_egg_appearance:
+        if i == 100:
+            midW = W // 2
+            midH = H // 2
+            safety_factor_t100 = (
+                sum(0 <= x < midW and 0 <= y < midH for x, y in state.values())
+                * sum(midW < x < W and 0 <= y < midH for x, y in state.values())
+                * sum(0 <= x < midW and midH < y < H for x, y in state.values())
+                * sum(midW < x < W and midH < y < H for x, y in state.values())
+            )
+        for id, props in enumerate(robots):
+            _ix, _iy, vx, vy = props
+            x, y = state[id]
+            state[id] = ((x + vx) % W, (y + vy) % H)
+        i += 1
+        if find_easter_egg:
+            if i % easter_egg_recurring == easter_egg_offset:
+                vdbg(state.values(), H, W)
+                print(i)
+                input("--- any key pls ---")
+    if display_easter_egg:
+        easter_egg = [
+            (y - 26, x - 23)
+            for x, y in state.values()
+            if 20 <= x <= 53 and 24 <= y <= 60
+        ]
+        max_y, max_x = max(easter_egg)
+        vdbg(easter_egg, max_y + 1, max_x + 1)
+        print("")
+    return safety_factor_t100, easter_egg_appearance
+
+
+if __name__ == "__main__":
+    with open("./input/14.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp, display_easter_egg=False)
+
+    print(p1)
+    print(p2)