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<!DOCTYPE html>
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<title>2020\day02.nim</title>
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<span><a href="..">🏡</a></span>
<span><code>2020\day02.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>
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<h1>--- Day 2: Password Philosophy ---</h1>
<p>from <a href="https://adventofcode.com/2020/day/2">original text</a></p>
<p>a list (your puzzle input) of <em>passwords</em>
(according to the corrupted database) and
<em>the corporate policy when that password was set</em>.</p>
<p>For example, suppose you have the following list:</p>
<pre><code class="nim hljs"><span class="hljs-keyword">let</span> example = <span class="hljs-string">"""1-3 a: abcde
1-3 b: cdefg
2-9 c: ccccccccc
"""</span>
<span class="hljs-keyword">echo</span> example</code></pre>
<pre><samp>1-3 a: abcde
1-3 b: cdefg
2-9 c: ccccccccc</samp></pre>
<p>Each line gives the password policy and then the password.
The password policy indicates the lowest and highest number of times
a given letter must appear for the password to be valid.
For example, 1-3 a means that the password must contain
a at least 1 time and at most 3 times.</p>
<p>In the above example, 2 passwords are valid.
The middle password, cdefg, is not;
it contains no instances of b, but needs at least 1.
The first and third passwords are valid:
they contain one a or nine c,
both within the limits of their respective policies.</p>
<p><em>How many passwords are valid</em> according to their policies?</p>
<h2>structure the data</h2>
<p>something I love about Nim (wrt to my usual language Python)
is that the first thing you do is structure your data (i.e. deciding types)
and that is solving half of the problem.</p>
<pre><code class="nim hljs"><span class="hljs-keyword">type</span>
<span class="hljs-type">Policy</span> = <span class="hljs-keyword">object</span>
min, max: <span class="hljs-type">Natural</span>
ch: <span class="hljs-built_in">char</span>
<span class="hljs-type">Row</span> = <span class="hljs-keyword">tuple</span>[policy: <span class="hljs-type">Policy</span>, password: <span class="hljs-built_in">string</span>]
<span class="hljs-type">Db</span> = <span class="hljs-built_in">seq</span>[<span class="hljs-type">Row</span>]</code></pre>
<p>and also that helps in naming.
how do I call the parse function? well, <em>parse</em>!</p>
<p>Do I want to extract parsing for the first row?
easy and I do not have to pick a new name!</p>
<pre><code class="nim hljs"><span class="hljs-keyword">func</span> parse(line: <span class="hljs-built_in">string</span>): <span class="hljs-type">Row</span> =
<span class="hljs-keyword">var</span>
i, j: <span class="hljs-built_in">int</span>
s, t: <span class="hljs-built_in">string</span>
<span class="hljs-keyword">if</span> <span class="hljs-keyword">not</span> scanf(line, <span class="hljs-string">"$i-$i $w: $w"</span>, i, j, s, t):
debugEcho <span class="hljs-string">"error while parsing: "</span> & line
<span class="hljs-keyword">if</span> s.len != <span class="hljs-number">1</span>:
debugEcho <span class="hljs-string">"error in s.len. s: "</span>, s, <span class="hljs-string">"; line: "</span>, line
<span class="hljs-literal">result</span>.policy.min = i
<span class="hljs-literal">result</span>.policy.max = j
<span class="hljs-literal">result</span>.policy.ch = s[<span class="hljs-number">0</span>]
<span class="hljs-literal">result</span>.password = t
<span class="hljs-keyword">proc</span> parse(lines: <span class="hljs-built_in">seq</span>[<span class="hljs-built_in">string</span>]): <span class="hljs-type">Db</span> =
<span class="hljs-keyword">for</span> i, line <span class="hljs-keyword">in</span> lines:
<span class="hljs-literal">result</span>.add parse(line)</code></pre>
<p>Also I love the fact that strscans prevents me to learn regular expressions.</p>
<p>Let's see how parsing work on base example:</p>
<pre><code class="nim hljs"><span class="hljs-keyword">echo</span> (parse example.strip.splitLines).join(<span class="hljs-string">"</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>)</code></pre>
<pre><samp>(policy: (min: 1, max: 3, ch: 'a'), password: "abcde")
(policy: (min: 1, max: 3, ch: 'b'), password: "cdefg")
(policy: (min: 2, max: 9, ch: 'c'), password: "ccccccccc")</samp></pre>
<p>ok, good. Now let's solve part1 (for this example)</p>
<h2>part 1</h2>
<pre><code class="nim hljs"><span class="hljs-keyword">func</span> isValid(r: <span class="hljs-type">Row</span>): <span class="hljs-built_in">bool</span> =
<span class="hljs-keyword">var</span> count: <span class="hljs-built_in">int</span>
<span class="hljs-keyword">for</span> c <span class="hljs-keyword">in</span> r.password:
<span class="hljs-keyword">if</span> c == r.policy.ch:
inc count
<span class="hljs-keyword">if</span> count >= r.policy.min <span class="hljs-keyword">and</span> count <= r.policy.max:
<span class="hljs-literal">true</span>
<span class="hljs-keyword">else</span>:
<span class="hljs-literal">false</span>
<span class="hljs-keyword">func</span> part1(input: <span class="hljs-built_in">string</span>): <span class="hljs-built_in">int</span> =
<span class="hljs-keyword">for</span> row <span class="hljs-keyword">in</span> parse(input.strip.splitLines):
<span class="hljs-keyword">if</span> row.isValid:
inc <span class="hljs-literal">result</span>
<span class="hljs-keyword">echo</span> part1 example
<span class="hljs-keyword">assert</span> example.part1 == <span class="hljs-number">2</span></code></pre>
<pre><samp>2</samp></pre>
<p>now it's time to get the <em class="star">*</em>!</p>
<pre><code class="nim hljs"><span class="hljs-keyword">echo</span> part1 <span class="hljs-string">"2020/input02.txt"</span>.readFile</code></pre>
<pre><samp>445</samp></pre>
<p><em>ok, I did spend a bit of time debugging here, just to find out that I forgot to past content in file...</em></p>
<p>That's the right answer! You are <em class="star">one gold star</em> closer to saving your vacation.</p>
<h2>--- Part 2 ---</h2>
<p>from <a href="https://adventofcode.com/2020/day/2">original text</a></p>
<p>Each policy actually describes <em>two positions in the password</em>,
where 1 means the first character, 2 means the second character,
and so on. (Be careful; Toboggan Corporate Policies have no
concept of "index zero"!)
<em>Exactly one of these positions</em> must contain the given letter.
Other occurrences of the letter are irrelevant
for the purposes of policy enforcement.</p>
<pre><code class="nim hljs"><span class="hljs-keyword">func</span> isValid2(r: <span class="hljs-type">Row</span>): <span class="hljs-built_in">bool</span> =
<span class="hljs-keyword">var</span> count: <span class="hljs-built_in">int</span>
<span class="hljs-keyword">if</span> r.password[r.policy.min - <span class="hljs-number">1</span>] == r.policy.ch:
inc count
<span class="hljs-keyword">if</span> r.password[r.policy.max - <span class="hljs-number">1</span>] == r.policy.ch:
inc count
count == <span class="hljs-number">1</span>
<span class="hljs-keyword">func</span> part2(input: <span class="hljs-built_in">string</span>): <span class="hljs-built_in">int</span> =
<span class="hljs-keyword">for</span> row <span class="hljs-keyword">in</span> parse(input.strip.splitLines):
<span class="hljs-keyword">if</span> row.isValid2:
inc <span class="hljs-literal">result</span>
<span class="hljs-keyword">echo</span> <span class="hljs-string">"example: "</span>:
part2 example
<span class="hljs-keyword">echo</span> <span class="hljs-string">"part2: "</span>:
part2 <span class="hljs-string">"2020/input02.txt"</span>.readFile</code></pre>
<pre><samp>example: 1
part2: 491</samp></pre>
<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
nbInit
nbText: <span class="hljs-string">"# --- Day 2: Password Philosophy ---"</span>
nbText: <span class="hljs-string">"""from [original text](https://adventofcode.com/2020/day/2)
a list (your puzzle input) of _passwords_
(according to the corrupted database) and
_the corporate policy when that password was set_.
For example, suppose you have the following list:
"""</span>
nbCode:
<span class="hljs-keyword">let</span> example = <span class="hljs-string">"""1-3 a: abcde
1-3 b: cdefg
2-9 c: ccccccccc
"""</span>
<span class="hljs-keyword">echo</span> example
nbText: <span class="hljs-string">"""
Each line gives the password policy and then the password.
The password policy indicates the lowest and highest number of times
a given letter must appear for the password to be valid.
For example, 1-3 a means that the password must contain
a at least 1 time and at most 3 times.
In the above example, 2 passwords are valid.
The middle password, cdefg, is not;
it contains no instances of b, but needs at least 1.
The first and third passwords are valid:
they contain one a or nine c,
both within the limits of their respective policies.
_How many passwords are valid_ according to their policies?"""</span>
nbText: <span class="hljs-string">"""## structure the data
something I love about Nim (wrt to my usual language Python)
is that the first thing you do is structure your data (i.e. deciding types)
and that is solving half of the problem.
"""</span>
nbCode:
<span class="hljs-keyword">type</span>
<span class="hljs-type">Policy</span> = <span class="hljs-keyword">object</span>
min, max: <span class="hljs-type">Natural</span>
ch: <span class="hljs-built_in">char</span>
<span class="hljs-type">Row</span> = <span class="hljs-keyword">tuple</span>[policy: <span class="hljs-type">Policy</span>, password: <span class="hljs-built_in">string</span>]
<span class="hljs-type">Db</span> = <span class="hljs-built_in">seq</span>[<span class="hljs-type">Row</span>]
nbText: <span class="hljs-string">"""and also that helps in naming.
how do I call the parse function? well, _parse_!
Do I want to extract parsing for the first row?
easy and I do not have to pick a new name!
"""</span>
nbCode:
<span class="hljs-keyword">func</span> parse(line: <span class="hljs-built_in">string</span>): <span class="hljs-type">Row</span> =
<span class="hljs-keyword">var</span>
i, j: <span class="hljs-built_in">int</span>
s, t: <span class="hljs-built_in">string</span>
<span class="hljs-keyword">if</span> <span class="hljs-keyword">not</span> scanf(line, <span class="hljs-string">"$i-$i $w: $w"</span>, i, j, s, t):
debugEcho <span class="hljs-string">"error while parsing: "</span> & line
<span class="hljs-keyword">if</span> s.len != <span class="hljs-number">1</span>:
debugEcho <span class="hljs-string">"error in s.len. s: "</span>, s, <span class="hljs-string">"; line: "</span>, line
<span class="hljs-literal">result</span>.policy.min = i
<span class="hljs-literal">result</span>.policy.max = j
<span class="hljs-literal">result</span>.policy.ch = s[<span class="hljs-number">0</span>]
<span class="hljs-literal">result</span>.password = t
<span class="hljs-keyword">proc</span> parse(lines: <span class="hljs-built_in">seq</span>[<span class="hljs-built_in">string</span>]): <span class="hljs-type">Db</span> =
<span class="hljs-keyword">for</span> i, line <span class="hljs-keyword">in</span> lines:
<span class="hljs-literal">result</span>.add parse(line)
nbText: <span class="hljs-string">"""
Also I love the fact that strscans prevents me to learn regular expressions.
Let's see how parsing work on base example:
"""</span>
nbCode:
<span class="hljs-keyword">echo</span> (parse example.strip.splitLines).join(<span class="hljs-string">"</span><span class="hljs-meta">\n</span><span class="hljs-string">"</span>)
nbText: <span class="hljs-string">"""
ok, good. Now let's solve part1 (for this example)
## part 1
"""</span>
nbCode:
<span class="hljs-keyword">func</span> isValid(r: <span class="hljs-type">Row</span>): <span class="hljs-built_in">bool</span> =
<span class="hljs-keyword">var</span> count: <span class="hljs-built_in">int</span>
<span class="hljs-keyword">for</span> c <span class="hljs-keyword">in</span> r.password:
<span class="hljs-keyword">if</span> c == r.policy.ch:
inc count
<span class="hljs-keyword">if</span> count >= r.policy.min <span class="hljs-keyword">and</span> count <= r.policy.max:
<span class="hljs-literal">true</span>
<span class="hljs-keyword">else</span>:
<span class="hljs-literal">false</span>
<span class="hljs-keyword">func</span> part1(input: <span class="hljs-built_in">string</span>): <span class="hljs-built_in">int</span> =
<span class="hljs-keyword">for</span> row <span class="hljs-keyword">in</span> parse(input.strip.splitLines):
<span class="hljs-keyword">if</span> row.isValid: inc <span class="hljs-literal">result</span>
<span class="hljs-keyword">echo</span> part1 example
<span class="hljs-keyword">assert</span> example.part1 == <span class="hljs-number">2</span>
nbText: &<span class="hljs-string">"now it's time to get the {star}!"</span>
nbCode:
<span class="hljs-keyword">echo</span> part1 <span class="hljs-string">"2020/input02.txt"</span>.readFile
nbText: <span class="hljs-string">"*ok, I did spend a bit of time debugging here, just to find out that I forgot to past content in file...*"</span>
gotTheStar
nbText: <span class="hljs-string">"## --- Part 2 ---"</span>
nbText: <span class="hljs-string">"""from [original text](https://adventofcode.com/2020/day/2)
Each policy actually describes _two positions in the password_,
where 1 means the first character, 2 means the second character,
and so on. (Be careful; Toboggan Corporate Policies have no
concept of "index zero"!)
_Exactly one of these positions_ must contain the given letter.
Other occurrences of the letter are irrelevant
for the purposes of policy enforcement.
"""</span>
nbCode:
<span class="hljs-keyword">func</span> isValid2(r: <span class="hljs-type">Row</span>): <span class="hljs-built_in">bool</span> =
<span class="hljs-keyword">var</span> count: <span class="hljs-built_in">int</span>
<span class="hljs-keyword">if</span> r.password[r.policy.min - <span class="hljs-number">1</span>] == r.policy.ch:
inc count
<span class="hljs-keyword">if</span> r.password[r.policy.max - <span class="hljs-number">1</span>] == r.policy.ch:
inc count
count == <span class="hljs-number">1</span>
<span class="hljs-keyword">func</span> part2(input: <span class="hljs-built_in">string</span>): <span class="hljs-built_in">int</span> =
<span class="hljs-keyword">for</span> row <span class="hljs-keyword">in</span> parse(input.strip.splitLines):
<span class="hljs-keyword">if</span> row.isValid2: inc <span class="hljs-literal">result</span>
<span class="hljs-keyword">echo</span> <span class="hljs-string">"example: "</span>: part2 example
<span class="hljs-keyword">echo</span> <span class="hljs-string">"part2: "</span>: part2 <span class="hljs-string">"2020/input02.txt"</span>.readFile
gotTheStar
<span class="hljs-comment"># You have completed Day 2!</span>
nbSave</code></pre>
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