From 6f0383f0b1dd202b11758da3448aec99dc3084fc Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Fri, 21 Apr 2023 17:05:03 +0200
Subject: Add day 3

---
 2022/day3/src/lib.rs | 129 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 2022/day3/src/lib.rs

(limited to '2022/day3/src/lib.rs')

diff --git a/2022/day3/src/lib.rs b/2022/day3/src/lib.rs
new file mode 100644
index 0000000..0eadb0d
--- /dev/null
+++ b/2022/day3/src/lib.rs
@@ -0,0 +1,129 @@
+use std::collections::{HashMap, HashSet};
+
+pub fn part1(input: &str) -> usize {
+    let mut tot: usize = 0;
+
+    let lines = input
+        .lines()
+        .map(|x| String::from(x))
+        .collect::<Vec<String>>();
+
+    let mut map = HashMap::<char, usize>::new();
+
+    for (i, ch) in ('a'..='z').enumerate() {
+        map.insert(ch, i + 1);
+    }
+    for (i, ch) in ('A'..='Z').enumerate() {
+        map.insert(ch, i + 27);
+    }
+
+    for line in lines {
+        let half = line.len() / 2;
+
+        let (l, r) = (&line[0..half], &line[half..]);
+
+        'o: for ch in l.chars() {
+            for ch2 in r.chars() {
+                if ch == ch2 {
+                    tot += map[&ch];
+                    break 'o;
+                }
+            }
+        }
+    }
+
+    tot
+}
+
+pub fn part2(input: &str) -> usize {
+    let mut tot: usize = 0;
+
+    let lines = input
+        .lines()
+        .map(|x| String::from(x))
+        .collect::<Vec<String>>();
+
+    let mut map = HashMap::<char, usize>::new();
+
+    for (i, ch) in ('a'..='z').enumerate() {
+        map.insert(ch, i + 1);
+    }
+    for (i, ch) in ('A'..='Z').enumerate() {
+        map.insert(ch, i + 27);
+    }
+
+    let n = lines.len() / 3;
+    let mut group_of_3 = Vec::<Vec<String>>::with_capacity(n);
+    for _ in 0..n {
+        group_of_3.push(vec![]);
+    }
+
+    let mut idx = 0;
+
+    for (i, line) in lines.iter().enumerate() {
+        if i % 3 == 0 && i != 0 {
+            idx += 1;
+        }
+        group_of_3[idx].push(line.to_string());
+    }
+
+    for g in group_of_3 {
+        let mut h1 = HashSet::new();
+        let mut h2 = HashSet::new();
+        for ch in g[0].chars() {
+            h1.insert(ch);
+        }
+        for ch in g[1].chars() {
+            h2.insert(ch);
+        }
+        for ch in g[2].chars() {
+            if h1.contains(&ch) && h2.contains(&ch) {
+                tot += map[&ch];
+                break;
+            }
+        }
+    }
+
+    tot
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_example() {
+        let data = include_str!("../example.txt");
+
+        let result = part1(data);
+
+        assert_eq!(result, 157);
+    }
+
+    #[test]
+    fn test_input() {
+        let data = include_str!("../input.txt");
+
+        let result = part1(data);
+
+        assert_eq!(result, 7428);
+    }
+
+    #[test]
+    fn test_example_2() {
+        let data = include_str!("../example.txt");
+
+        let result = part2(data);
+
+        assert_eq!(result, 70);
+    }
+
+    #[test]
+    fn test_input_2() {
+        let data = include_str!("../input.txt");
+
+        let result = part2(data);
+
+        assert_eq!(result, 2650);
+    }
+}
-- 
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