feat: add day3

data/examples/03.txt

@@ -0,0 +1,6 @@
+ 5 10 25
+  3  4   5
+1 2 3
+25 5 10
+6 8   10
+30  10 20

src/bin/03.rs

@@ -0,0 +1,92 @@
+advent_of_code::solution!(3);
+
+fn parse_line(input: &str) -> [u32; 3] {
+    let nb: Result<Vec<u32>, _> = input
+        .split_whitespace()
+        .map(str::parse)
+        .collect();
+    if let Ok(nb) = nb {
+        if nb.len() == 3 {
+            return [nb[0], nb[1], nb[2]];
+        }
+    }
+    println!("input was: {:?}", input);
+    panic!("invalid input");
+}
+
+fn parse_input(input: &str) -> Vec<[u32; 3]> {
+    input
+        .strip_suffix("\n")
+        .unwrap_or(input)
+        .split("\n")
+        .map(parse_line)
+        .collect()
+}
+
+fn parse_input_p2(input: &str) -> Vec<[u32; 3]> {
+    parse_input(input)
+        .chunks(3)
+        .map(|c| {
+            let v = c.to_vec();
+            if v.len() != 3 {
+                println!("{:?}", v);
+                panic!("invalid input (line count should be multiple of 3)")
+            }
+            let vs = [v[0], v[1], v[2]];
+            // LAAAAAAZY... Could have transposed
+            let [
+                [ta1, tb1, tc1],
+                [ta2, tb2, tc2],
+                [ta3, tb3, tc3],
+            ] = vs;
+            [
+                [ta1, ta2, ta3],
+                [tb1, tb2, tb3],
+                [tc1, tc2, tc3],
+            ].to_vec()
+        })
+        .flatten()
+        .collect()
+}
+
+fn is_valid(triangle: &[u32; 3]) -> bool {
+    let &[a, b, c] = triangle;
+    (a + b) > c
+        && (b + c) > a
+        && (c + a) > b
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    Some(
+        parse_input(input)
+            .into_iter()
+            .filter(is_valid)
+            .count() as u32
+    )
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    Some(
+        parse_input_p2(input)
+            .into_iter()
+            .filter(is_valid)
+            .count() as u32
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(2));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(2));
+    }
+}