day2, pt1

Cargo.lock

@@ -9,6 +9,10 @@ dependencies = [
  "winnow",
 ]
 
+[[package]]
+name = "day02"
+version = "0.1.0"
+
 [[package]]
 name = "memchr"
 version = "2.7.4"

Cargo.toml

@@ -1,6 +1,6 @@
 [workspace]
 resolver = "2"
-members = ["day01"]
+members = ["day01", "day02"]
 
 [workspace.dependencies]
 winnow = "0.6"

day02/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day02"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

day02/src/main.rs

@@ -0,0 +1,77 @@
+fn main() {
+    let input = std::fs::read_to_string("input").unwrap();
+    println!("{}", pt1(&input));
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+enum Sign {
+    Pos,
+    Neg,
+}
+
+impl Sign {
+    fn new(s: i64) -> Self {
+        if s.signum() < 0 { Sign::Neg } else { Sign::Pos }
+    }
+}
+
+fn pt1(input: &str) -> usize {
+    let input = parse(input);
+    let mut safe = 0;
+    for line in input.iter() {
+        let mut dir = None;
+        let mut last = None;
+        let mut lsafe = true;
+        for v in line.iter() {
+            if let Some(l) = last {
+                last = Some(v);
+                let d = v - l;
+                let s = Sign::new(d);
+                if let Some(p) = dir {
+                    if p != s {
+                        lsafe = false;
+                        break;
+                    }
+                }
+                dir = Some(s);
+                if d.abs() > 3 || d.abs() < 1 {
+                    lsafe = false;
+                    break;
+                }
+            } else {
+                last = Some(v);
+            }
+        }
+        if lsafe {
+            safe += 1;
+        }
+    }
+
+    safe
+}
+
+fn parse(input: &str) -> Vec<Vec<i64>> {
+    let mut lines = Vec::new();
+    for line in input.split("\n").filter(|s| !s.is_empty()) {
+        let l = line.split(' ').map(|n| n.parse().unwrap()).collect();
+        lines.push(l);
+    }
+    lines
+}
+
+mod test {
+    use super::*;
+
+    static INPUT: &str = "7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9";
+
+    #[test]
+    fn tp1() {
+        let safe = pt1(INPUT);
+        assert_eq!(2, safe);
+    }
+}