day 4

2022/Cargo.toml

@@ -19,6 +19,10 @@ path = "src/day2.rs"
 name = "day3"
 path = "src/day3.rs"
 
+[[bin]]
+name = "day4"
+path = "src/day4.rs"
+
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]

2022/src/day4.rs

@@ -0,0 +1,89 @@
+const DATA: &'static str = include_str!("../data/day4.txt");
+// const DATA: &'static str = "
+// 2-4,6-8
+// 2-3,4-5
+// 5-7,7-9
+// 2-8,3-7
+// 6-6,4-6
+// 2-6,4-8
+// ";
+
+
+#[derive(Debug)]
+enum DataError {
+    NotANumber,
+    NotAPair,
+    NotARange,
+}
+
+
+struct Range {
+    start: u32,
+    end: u32,
+}
+
+impl Range {
+    fn contains(&self, other: &Range) -> bool {
+        self.start <= other.start && self.end >= other.end
+    }
+
+    fn overlaps(&self, other: &Range) -> bool {
+        // what if self.start == other.start or self.end == other.end?
+        if self.start <= other.start && self.end >= other.start {
+            return true;
+        }
+
+        if self.start <= other.end && self.end >= other.end {
+            return true;
+        }
+        false
+    }
+}
+
+impl std::str::FromStr for Range {
+    type Err = DataError;
+
+    fn from_str(s: &str) -> Result<Range, DataError> {
+        let mut bounds = s.split('-');
+
+        let start = bounds.next()
+            .ok_or(DataError::NotARange)?
+            .parse::<u32>()
+            .map_err(|_e| DataError::NotANumber)?;
+        let end = bounds.next()
+            .ok_or(DataError::NotARange)?
+            .parse::<u32>()
+            .map_err(|_e| DataError::NotANumber)?;
+
+        Ok(Range {start, end})
+    }
+}
+
+
+fn main() -> Result<(), DataError> {
+    let ranges = DATA.trim()
+        .lines()
+        .map(|line| {
+            let mut pairs = line.split(',');
+            let left: Range = pairs.next()
+                .ok_or(DataError::NotAPair)?
+                .parse()?;
+            let right: Range = pairs.next()
+                .ok_or(DataError::NotAPair)?
+                .parse()?;
+            Ok((left, right))
+        })
+        .collect::<Result<Vec<(Range, Range)>, DataError>>()?;
+
+    let total_supersets = ranges.iter()
+        .filter(|(a, b)| a.contains(b) || b.contains(a))
+        .count();
+    println!("Part 1: {total_supersets}");
+
+    let total_overlaps = ranges.iter()
+        .filter(|(a, b)| a.overlaps(b) || b.contains(a) || a.contains(b))
+        .count();
+    println!("Part 2: {total_overlaps}");
+
+    Ok(())
+}