commiting day4

day4/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day4"
+version = "0.1.0"

day4/Cargo.toml

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+[package]
+name = "day4"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day4/src/main.rs

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+use std::fs::File;
+use std::io::{prelude::*, BufReader};
+
+fn main() -> std::io::Result<()> {
+    //Read in file
+    let file = File::open("input")?;
+    let reader = BufReader::new(file);
+
+    let value = reader
+        .lines()
+        .map(|line| {
+            let line = line.unwrap();
+            // split and parse
+            let (a, b) = match line.split(',').take(2).collect::<Vec<&str>>()[..] {
+                [a, b] => (
+                    a.split('-')
+                        .take(2)
+                        .map(|x| x.parse::<i32>().unwrap())
+                        .collect::<Vec<i32>>(),
+                    b.split('-')
+                        .take(2)
+                        .map(|x| x.parse::<i32>().unwrap())
+                        .collect::<Vec<i32>>(),
+                ),
+                _ => panic!("no good"),
+            };
+            (
+                // part 1 wholly overlapping
+                i32::from((a[0] <= b[0] && a[1] >= b[1]) || (a[0] >= b[0] && a[1] <= b[1])),
+                // part 2 any overlapping
+                i32::from(
+                    (a[0] >= b[0] && a[0] <= b[1])
+                        || (a[1] >= b[0] && a[1] <= b[1])
+                        || (b[0] >= a[0] && b[0] <= a[1])
+                        || (b[1] >= a[0] && b[1] <= a[1]),
+                ),
+            )
+        })
+        // using folding instead of sum() so that we can do both parts in one call
+        .fold((0, 0), |mut acc: (i32, i32), x| {
+            acc.0 += x.0;
+            acc.1 += x.1;
+            acc
+        });
+    println!("Part 1: {}", value.0);
+    println!("Part 2: {}", value.1);
+
+    Ok(())
+}