2022 Day 4 in Rust

2022/day4.rs

@@ -0,0 +1,57 @@
+use std::fs::File;
+use std::io::{self, BufRead};
+
+#[derive(Debug, Copy, Clone)]
+struct Range{ min: i32, max: i32 }
+
+impl Range {
+    fn from_string(s: &str) -> Option<Range> {
+        let mut parts = s.split('-');
+        let min: i32 = parts.next().map(|s| s.parse::<i32>().ok()).flatten()?;
+        let max: i32 = parts.next().map(|s| s.parse::<i32>().ok()).flatten()?;
+        Some(Range{min: min,max: max})
+    }
+    
+    fn contains(self, other: Range) -> bool {
+        self.min <= other.min && other.max <= self.max
+    }
+    
+    fn contains_value(self, value: i32) -> bool {
+        self.min <= value && value <= self.max
+    }
+    
+    fn overlaps(self, other: Range) -> bool {
+        self.contains_value(other.min) || 
+            self.contains_value(other.max) ||
+            other.contains_value(self.min) ||
+            other.contains_value(self.max)
+    }
+}
+
+fn main() {
+    let file = File::open("day4.input")
+        .expect("Can open file");
+
+    let mut contained = 0;
+    let mut overlapping = 0;
+    
+    for l in io::BufReader::new(file).lines() {
+        let line = l.expect("Cannot read line");
+        let mut ranges = line.split(',').map(Range::from_string).flatten();
+        
+        let first = ranges.next().expect("Invalid input");
+        let second = ranges.next().expect("Invalid input");
+        
+        if first.contains(second) || second.contains(first) {
+            contained += 1;
+        }
+        
+        if first.overlaps(second) {
+            overlapping += 1
+        }
+    }
+    
+    println!("Part 1: Contained pairs   {}", contained);
+    println!("Part 2: Overlapping pairs {}", overlapping);
+}
+