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<!DOCTYPE html>
<html lang="en-us">
<head>
<title>2020\day17.nim</title>
<link rel="icon" href="data:image/svg+xml,<svg xmlns=%22http://www.w3.org/2000/svg%22 viewBox=%220 0 100 100%22><text y=%22.9em%22 font-size=%2280%22>🐳</text></svg>">
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a {
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<header>
<div class="nb-box">
<span><a href="..">🏡</a></span>
<span><code>2020\day17.nim</code></span>
<span><a href="https://github.com/pietroppeter/adventofnim"><svg aria-hidden="true" width="1.2em" height="1.2em" style="vertical-align: middle; fill: #fff" preserveAspectRatio="xMidYMid meet" viewBox="0 0 16 16"><path fill-rule="evenodd" d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0016 8c0-4.42-3.58-8-8-8z"></path></svg></a></span>
</div>
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</header><main>
<h2>2020, Day 17: Conway Cubes 🔲 🔳</h2>
<p>Today is about implementing game of life in 3 or 4 dimensions.
The usual thing to be careful about is to make a copy of the data structure you use to track active cells.</p>
<p>My implementation is really basic and part2 is just a modified version of part1.
The only highlight is a <code>Mat3</code> type and a <code>triple</code> iterator to implement <code>neighbours</code> iterator.</p>
<p>I did suffer a bit because it took a moment to find a bug
(I was forgetting to remove cubes that become inactive, I though I was starting from an empty buffer but I was not).</p>
<p>some imports and my inputs:</p>
<pre><code class="nim hljs"><span class="hljs-keyword">import</span>
sets, strutils, std / enumerate, strformat
<span class="hljs-keyword">let</span> example = <span class="hljs-string">""".#.
..#
###"""</span>
<span class="hljs-keyword">let</span> input = <span class="hljs-string">"""##..####
.###....
#.###.##
#....#..
...#..#.
#.#...##
..#.#.#.
.##...#."""</span></code></pre>
<p>Usual parsing:</p>
<pre><code class="nim hljs"><span class="hljs-keyword">type</span>
<span class="hljs-type">Vec3</span> = <span class="hljs-keyword">tuple</span>[x, y, z: <span class="hljs-built_in">int</span>]
<span class="hljs-type">Active</span> = <span class="hljs-type">HashSet</span>[<span class="hljs-type">Vec3</span>]
<span class="hljs-keyword">proc</span> parse(text: <span class="hljs-built_in">string</span>): <span class="hljs-type">Active</span> =
<span class="hljs-keyword">for</span> y, line <span class="hljs-keyword">in</span> enumerate(text.splitLines): <span class="hljs-comment">## why does this need enumerate?</span>
<span class="hljs-keyword">for</span> x, c <span class="hljs-keyword">in</span> line:
<span class="hljs-keyword">if</span> c == <span class="hljs-string">'#'</span>:
<span class="hljs-literal">result</span>.incl (x, y, <span class="hljs-number">0</span>)
<span class="hljs-keyword">echo</span> parse example</code></pre>
<pre><samp>{(x: 0, y: 2, z: 0), (x: 1, y: 2, z: 0), (x: 1, y: 0, z: 0), (x: 2, y: 1, z: 0), (x: 2, y: 2, z: 0)}</samp></pre>
<p>yes, I should have written a template for bbox, but I was lazy. Anyway I reproduced the vizualization:</p>
<pre><code class="nim hljs"><span class="hljs-keyword">func</span> bbox(a: <span class="hljs-type">Active</span>): (<span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>) =
<span class="hljs-keyword">var</span> xmin, xmax, ymin, ymax, zmin, zmax: <span class="hljs-built_in">int</span>
(xmin, ymin, zmin) = (<span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>, <span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>, <span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>)
(xmax, ymax, zmax) = (-<span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>, -<span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>, -<span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>)
<span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> a:
<span class="hljs-keyword">if</span> v.x < xmin:
xmin = v.x
<span class="hljs-keyword">if</span> v.x > xmax:
xmax = v.x
<span class="hljs-keyword">if</span> v.y < ymin:
ymin = v.y
<span class="hljs-keyword">if</span> v.y > ymax:
ymax = v.y
<span class="hljs-keyword">if</span> v.z < zmin:
zmin = v.z
<span class="hljs-keyword">if</span> v.z > zmax:
zmax = v.z
(xmin, xmax, ymin, ymax, zmin, zmax)
<span class="hljs-keyword">func</span> viz(a: <span class="hljs-type">Active</span>): <span class="hljs-built_in">string</span> =
<span class="hljs-keyword">let</span> (xmin, xmax, ymin, ymax, zmin, zmax) = bbox a
<span class="hljs-keyword">for</span> z <span class="hljs-keyword">in</span> zmin .. zmax:
<span class="hljs-literal">result</span>.add &<span class="hljs-string">"z= {z}, y in {ymin..ymax}, x in {xmin}..{xmax}</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>
<span class="hljs-keyword">for</span> y <span class="hljs-keyword">in</span> ymin .. ymax:
<span class="hljs-keyword">for</span> x <span class="hljs-keyword">in</span> xmin .. xmax:
<span class="hljs-keyword">if</span> (x, y, z) <span class="hljs-keyword">in</span> a:
<span class="hljs-literal">result</span>.add <span class="hljs-string">"#"</span>
<span class="hljs-keyword">else</span>:
<span class="hljs-literal">result</span>.add <span class="hljs-string">"."</span>
<span class="hljs-literal">result</span>.add <span class="hljs-string">"</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>
<span class="hljs-literal">result</span>.add <span class="hljs-string">"</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>
<span class="hljs-keyword">var</span> a = parse example
<span class="hljs-keyword">echo</span> viz(a)</code></pre>
<pre><samp>z= 0, y in 0 .. 2, x in 0..2
.#.
..#
###</samp></pre>
<p>Here is the only bit of creativity I had for today: a <code>Mat3</code> type and two iterators that help me generate the neighbours.</p>
<pre><code class="nim hljs"><span class="hljs-keyword">type</span>
<span class="hljs-type">Mat3</span> = <span class="hljs-keyword">tuple</span>[a, b, c: <span class="hljs-type">Vec3</span>]
<span class="hljs-keyword">func</span> `+`(v, w: <span class="hljs-type">Vec3</span>): <span class="hljs-type">Vec3</span> =
(v.x + w.x, v.y + w.y, v.z + w.z)
<span class="hljs-keyword">func</span> `*`(v, w: <span class="hljs-type">Vec3</span>): <span class="hljs-built_in">int</span> =
(v.x * w.x + v.y * w.y + v.z * w.z)
<span class="hljs-keyword">func</span> `*`(m: <span class="hljs-type">Mat3</span>; v: <span class="hljs-type">Vec3</span>): <span class="hljs-type">Vec3</span> =
(m.a * v, m.b * v, m.c * v)
<span class="hljs-keyword">iterator</span> triple(a: <span class="hljs-built_in">array</span>[<span class="hljs-number">3</span>, <span class="hljs-built_in">int</span>]): <span class="hljs-type">Vec3</span> =
<span class="hljs-keyword">for</span> x <span class="hljs-keyword">in</span> a:
<span class="hljs-keyword">for</span> y <span class="hljs-keyword">in</span> a:
<span class="hljs-keyword">for</span> z <span class="hljs-keyword">in</span> a:
<span class="hljs-keyword">yield</span> (x, y, z)
<span class="hljs-keyword">iterator</span> neighbours(v: <span class="hljs-type">Vec3</span>): <span class="hljs-type">Vec3</span> =
<span class="hljs-keyword">let</span> m: <span class="hljs-type">Mat3</span> = ((<span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>), (<span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-number">0</span>), (<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">1</span>))
<span class="hljs-keyword">for</span> u <span class="hljs-keyword">in</span> triple([-<span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-number">1</span>]):
<span class="hljs-keyword">if</span> u == (<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>):
<span class="hljs-keyword">continue</span>
<span class="hljs-keyword">yield</span> v + m * u
<span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> neighbours((<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>)):
<span class="hljs-keyword">echo</span> v</code></pre>
<pre><samp>(x: -1, y: -1, z: -1)
(x: -1, y: -1, z: 0)
(x: -1, y: -1, z: 1)
(x: -1, y: 0, z: -1)
(x: -1, y: 0, z: 0)
(x: -1, y: 0, z: 1)
(x: -1, y: 1, z: -1)
(x: -1, y: 1, z: 0)
(x: -1, y: 1, z: 1)
(x: 0, y: -1, z: -1)
(x: 0, y: -1, z: 0)
(x: 0, y: -1, z: 1)
(x: 0, y: 0, z: -1)
(x: 0, y: 0, z: 1)
(x: 0, y: 1, z: -1)
(x: 0, y: 1, z: 0)
(x: 0, y: 1, z: 1)
(x: 1, y: -1, z: -1)
(x: 1, y: -1, z: 0)
(x: 1, y: -1, z: 1)
(x: 1, y: 0, z: -1)
(x: 1, y: 0, z: 0)
(x: 1, y: 0, z: 1)
(x: 1, y: 1, z: -1)
(x: 1, y: 1, z: 0)
(x: 1, y: 1, z: 1)</samp></pre>
<p>This is the key function</p>
<pre><code class="nim hljs"><span class="hljs-keyword">proc</span> cycle(a: <span class="hljs-keyword">var</span> <span class="hljs-type">Active</span>) =
<span class="hljs-keyword">var</span> b = a
<span class="hljs-keyword">let</span> (xmin, xmax, ymin, ymax, zmin, zmax) = bbox a
<span class="hljs-keyword">var</span>
cnt: <span class="hljs-built_in">int</span>
w: <span class="hljs-type">Vec3</span>
<span class="hljs-keyword">for</span> x <span class="hljs-keyword">in</span> (xmin - <span class="hljs-number">1</span>) .. (xmax + <span class="hljs-number">1</span>):
<span class="hljs-keyword">for</span> y <span class="hljs-keyword">in</span> (ymin - <span class="hljs-number">1</span>) .. (ymax + <span class="hljs-number">1</span>):
<span class="hljs-keyword">for</span> z <span class="hljs-keyword">in</span> (zmin - <span class="hljs-number">1</span>) .. (zmax + <span class="hljs-number">1</span>):
cnt = <span class="hljs-number">0</span>
w = (x, y, z)
<span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> neighbours(w):
<span class="hljs-keyword">if</span> v <span class="hljs-keyword">in</span> a:
inc cnt
<span class="hljs-keyword">if</span> w <span class="hljs-keyword">in</span> a <span class="hljs-keyword">and</span> cnt <span class="hljs-keyword">in</span> [<span class="hljs-number">2</span>, <span class="hljs-number">3</span>]:
b.incl w
<span class="hljs-keyword">else</span>: <span class="hljs-comment">## I was forgetting this branch</span>
b.excl w
<span class="hljs-keyword">if</span> w <span class="hljs-keyword">notin</span> a <span class="hljs-keyword">and</span> cnt == <span class="hljs-number">3</span>:
b.incl w
a = b</code></pre>
<p>Reproducing first 3 loops for the example:</p>
<pre><code class="nim hljs"><span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> <span class="hljs-number">1</span> .. <span class="hljs-number">3</span>:
cycle a
<span class="hljs-keyword">echo</span> viz(a)
<span class="hljs-keyword">echo</span> <span class="hljs-string">"---</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span></code></pre>
<pre><samp>z= -1, y in 1 .. 3, x in 0..2
#..
..#
.#.
z= 0, y in 1 .. 3, x in 0..2
#.#
.##
.#.
z= 1, y in 1 .. 3, x in 0..2
#..
..#
.#.
---
z= -2, y in 0 .. 4, x in -1..3
.....
.....
..#..
.....
.....
z= -1, y in 0 .. 4, x in -1..3
..#..
.#..#
....#
.#...
.....
z= 0, y in 0 .. 4, x in -1..3
##...
##...
#....
....#
.###.
z= 1, y in 0 .. 4, x in -1..3
..#..
.#..#
....#
.#...
.....
z= 2, y in 0 .. 4, x in -1..3
.....
.....
..#..
.....
.....
---
z= -2, y in -1 .. 5, x in -2..4
.......
.......
..##...
..###..
.......
.......
.......
z= -1, y in -1 .. 5, x in -2..4
..#....
...#...
#......
.....##
.#...#.
..#.#..
...#...
z= 0, y in -1 .. 5, x in -2..4
...#...
.......
#......
.......
.....##
.##.#..
...#...
z= 1, y in -1 .. 5, x in -2..4
..#....
...#...
#......
.....##
.#...#.
..#.#..
...#...
z= 2, y in -1 .. 5, x in -2..4
.......
.......
..##...
..###..
.......
.......
.......
---</samp></pre>
<p>solving the example</p>
<pre><code class="nim hljs"><span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> <span class="hljs-number">1</span> .. <span class="hljs-number">3</span>:
cycle a
<span class="hljs-keyword">echo</span> a.len <span class="hljs-comment">## 112</span></code></pre>
<pre><samp>112</samp></pre>
<p>Finally, let's go for the input:</p>
<pre><code class="nim hljs">a = parse input
<span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> <span class="hljs-number">1</span> .. <span class="hljs-number">6</span>:
cycle a
<span class="hljs-keyword">echo</span> <span class="hljs-string">"part 1:"</span>, a.len</code></pre>
<pre><samp>part 1:209</samp></pre>
<p>That's the right answer! You are <em class="star">one gold star</em> closer to saving your vacation.</p>
<p>Part 2 is a straightforward change from part 1.
You can look it up in the repo (I named for fourth dimension <code>q</code> because I wanted to keep using <code>w</code> for vector).</p>
<p>That's the right answer! You are <em class="star">one gold star</em> closer to saving your vacation.</p>
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<pre><code class="nim hljs"><span class="hljs-keyword">import</span> nimib, animu, nimoji
nbInit
nbText: <span class="hljs-string">"""## 2020, Day 17: Conway Cubes :black_square_button: :white_square_button:
Today is about implementing game of life in 3 or 4 dimensions.
The usual thing to be careful about is to make a copy of the data structure you use to track active cells.
My implementation is really basic and part2 is just a modified version of part1.
The only highlight is a `Mat3` type and a `triple` iterator to implement `neighbours` iterator.
I did suffer a bit because it took a moment to find a bug
(I was forgetting to remove cubes that become inactive, I though I was starting from an empty buffer but I was not).
"""</span>.emojize
nbText: <span class="hljs-string">"some imports and my inputs:"</span>
nbCode:
<span class="hljs-keyword">import</span> sets, strutils, std/enumerate, strformat
<span class="hljs-keyword">let</span> example = <span class="hljs-string">""".#.
..#
###"""</span>
<span class="hljs-keyword">let</span> input = <span class="hljs-string">"""##..####
.###....
#.###.##
#....#..
...#..#.
#.#...##
..#.#.#.
.##...#."""</span>
nbText: <span class="hljs-string">"Usual parsing:"</span>
nbCode:
<span class="hljs-keyword">type</span>
<span class="hljs-type">Vec3</span> = <span class="hljs-keyword">tuple</span>[x,y,z: <span class="hljs-built_in">int</span>]
<span class="hljs-type">Active</span> = <span class="hljs-type">HashSet</span>[<span class="hljs-type">Vec3</span>]
<span class="hljs-keyword">proc</span> parse(text: <span class="hljs-built_in">string</span>): <span class="hljs-type">Active</span> =
<span class="hljs-keyword">for</span> y, line <span class="hljs-keyword">in</span> enumerate(text.splitLines): <span class="hljs-comment">## why does this need enumerate?</span>
<span class="hljs-keyword">for</span> x, c <span class="hljs-keyword">in</span> line:
<span class="hljs-keyword">if</span> c == <span class="hljs-string">'#'</span>:
<span class="hljs-literal">result</span>.incl (x, y, <span class="hljs-number">0</span>)
<span class="hljs-keyword">echo</span> parse example
nbText: <span class="hljs-string">"yes, I should have written a template for bbox, but I was lazy. Anyway I reproduced the vizualization:"</span>
nbCode:
<span class="hljs-keyword">func</span> bbox(a: <span class="hljs-type">Active</span>): (<span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>, <span class="hljs-built_in">int</span>) =
<span class="hljs-keyword">var</span> xmin, xmax, ymin, ymax, zmin, zmax: <span class="hljs-built_in">int</span>
(xmin, ymin, zmin) = (<span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>, <span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>, <span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>)
(xmax, ymax, zmax) = (-<span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>, -<span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>, -<span class="hljs-built_in">int</span>.<span class="hljs-keyword">high</span>)
<span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> a:
<span class="hljs-keyword">if</span> v.x < xmin:
xmin = v.x
<span class="hljs-keyword">if</span> v.x > xmax:
xmax = v.x
<span class="hljs-keyword">if</span> v.y < ymin:
ymin = v.y
<span class="hljs-keyword">if</span> v.y > ymax:
ymax = v.y
<span class="hljs-keyword">if</span> v.z < zmin:
zmin = v.z
<span class="hljs-keyword">if</span> v.z > zmax:
zmax = v.z
(xmin, xmax, ymin, ymax, zmin, zmax)
<span class="hljs-keyword">func</span> viz(a: <span class="hljs-type">Active</span>): <span class="hljs-built_in">string</span> =
<span class="hljs-keyword">let</span> (xmin, xmax, ymin, ymax, zmin, zmax) = bbox a
<span class="hljs-keyword">for</span> z <span class="hljs-keyword">in</span> zmin..zmax:
<span class="hljs-literal">result</span>.add &<span class="hljs-string">"z= {z}, y in {ymin..ymax}, x in {xmin}..{xmax}</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>
<span class="hljs-keyword">for</span> y <span class="hljs-keyword">in</span> ymin..ymax:
<span class="hljs-keyword">for</span> x <span class="hljs-keyword">in</span> xmin..xmax:
<span class="hljs-keyword">if</span> (x, y, z) <span class="hljs-keyword">in</span> a:
<span class="hljs-literal">result</span>.add <span class="hljs-string">"#"</span>
<span class="hljs-keyword">else</span>:
<span class="hljs-literal">result</span>.add <span class="hljs-string">"."</span>
<span class="hljs-literal">result</span>.add <span class="hljs-string">"</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>
<span class="hljs-literal">result</span>.add <span class="hljs-string">"</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>
<span class="hljs-keyword">var</span> a = parse example
<span class="hljs-keyword">echo</span> viz(a)
nbText: <span class="hljs-string">"Here is the only bit of creativity I had for today: a `Mat3` type and two iterators that help me generate the neighbours."</span>
nbCode:
<span class="hljs-keyword">type</span>
<span class="hljs-type">Mat3</span> = <span class="hljs-keyword">tuple</span>[a, b, c: <span class="hljs-type">Vec3</span>]
<span class="hljs-keyword">func</span> `+`(v, w: <span class="hljs-type">Vec3</span>): <span class="hljs-type">Vec3</span> = (v.x + w.x, v.y + w.y, v.z + w.z)
<span class="hljs-keyword">func</span> `*`(v, w: <span class="hljs-type">Vec3</span>): <span class="hljs-built_in">int</span> = (v.x * w.x + v.y * w.y + v.z * w.z)
<span class="hljs-keyword">func</span> `*`(m: <span class="hljs-type">Mat3</span>, v: <span class="hljs-type">Vec3</span>): <span class="hljs-type">Vec3</span> = (m.a*v, m.b*v, m.c*v)
<span class="hljs-keyword">iterator</span> triple(a: <span class="hljs-built_in">array</span>[<span class="hljs-number">3</span>, <span class="hljs-built_in">int</span>]): <span class="hljs-type">Vec3</span> =
<span class="hljs-keyword">for</span> x <span class="hljs-keyword">in</span> a:
<span class="hljs-keyword">for</span> y <span class="hljs-keyword">in</span> a:
<span class="hljs-keyword">for</span> z <span class="hljs-keyword">in</span> a:
<span class="hljs-keyword">yield</span> (x, y, z)
<span class="hljs-keyword">iterator</span> neighbours(v: <span class="hljs-type">Vec3</span>): <span class="hljs-type">Vec3</span> =
<span class="hljs-keyword">let</span> m: <span class="hljs-type">Mat3</span> = ((<span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>), (<span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-number">0</span>), (<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">1</span>))
<span class="hljs-keyword">for</span> u <span class="hljs-keyword">in</span> triple([-<span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-number">1</span>]):
<span class="hljs-keyword">if</span> u == (<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>):
<span class="hljs-keyword">continue</span>
<span class="hljs-keyword">yield</span> v + m*u
<span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> neighbours((<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>)):
<span class="hljs-keyword">echo</span> v
nbText: <span class="hljs-string">"This is the key function"</span>
nbCode:
<span class="hljs-keyword">proc</span> cycle(a: <span class="hljs-keyword">var</span> <span class="hljs-type">Active</span>) =
<span class="hljs-keyword">var</span> b = a
<span class="hljs-keyword">let</span>
(xmin, xmax, ymin, ymax, zmin, zmax) = bbox a
<span class="hljs-keyword">var</span>
cnt: <span class="hljs-built_in">int</span>
w: <span class="hljs-type">Vec3</span>
<span class="hljs-keyword">for</span> x <span class="hljs-keyword">in</span> (xmin - <span class="hljs-number">1</span>)..(xmax + <span class="hljs-number">1</span>):
<span class="hljs-keyword">for</span> y <span class="hljs-keyword">in</span> (ymin - <span class="hljs-number">1</span>)..(ymax + <span class="hljs-number">1</span>):
<span class="hljs-keyword">for</span> z <span class="hljs-keyword">in</span> (zmin - <span class="hljs-number">1</span>)..(zmax + <span class="hljs-number">1</span>):
cnt = <span class="hljs-number">0</span>
w = (x, y, z)
<span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> neighbours(w):
<span class="hljs-keyword">if</span> v <span class="hljs-keyword">in</span> a:
inc cnt
<span class="hljs-keyword">if</span> w <span class="hljs-keyword">in</span> a <span class="hljs-keyword">and</span> cnt <span class="hljs-keyword">in</span> [<span class="hljs-number">2</span>, <span class="hljs-number">3</span>]:
b.incl w
<span class="hljs-keyword">else</span>: <span class="hljs-comment">## I was forgetting this branch</span>
b.excl w
<span class="hljs-keyword">if</span> w <span class="hljs-keyword">notin</span> a <span class="hljs-keyword">and</span> cnt == <span class="hljs-number">3</span>:
b.incl w
a = b
nbText: <span class="hljs-string">"Reproducing first 3 loops for the example:"</span>
nbCode:
<span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> <span class="hljs-number">1.</span>.<span class="hljs-number">3</span>:
cycle a
<span class="hljs-keyword">echo</span> viz(a)
<span class="hljs-keyword">echo</span> <span class="hljs-string">"---</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>
nbText: <span class="hljs-string">"solving the example"</span>
nbCode:
<span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> <span class="hljs-number">1.</span>.<span class="hljs-number">3</span>:
cycle a
<span class="hljs-keyword">echo</span> a.len <span class="hljs-comment">## 112</span>
nbText: <span class="hljs-string">"Finally, let's go for the input:"</span>
nbCode:
a = parse input
<span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> <span class="hljs-number">1.</span>.<span class="hljs-number">6</span>:
cycle a
<span class="hljs-keyword">echo</span> <span class="hljs-string">"part 1:"</span>, a.len
gotTheStar
nbText: <span class="hljs-string">"""
Part 2 is a straightforward change from part 1.
You can look it up in the repo (I named for fourth dimension `q` because I wanted to keep using `w` for vector).
"""</span>
gotTheStar
nbSave</code></pre>
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