Restructure folders

2023/day1/part1/.gitignore

@@ -0,0 +1 @@
+/target

2023/day1/part1/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day1"
+version = "0.1.0"

2023/day1/part1/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day1"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2023/day1/part1/src/main.rs

@@ -0,0 +1,44 @@
+fn main() {
+    let input = std::fs::read_to_string("./input").unwrap();
+
+    struct FirstLast {
+        first: Option<u32>,
+        last: Option<u32>,
+    }
+
+    impl FirstLast {
+        fn new() -> Self {
+            Self {
+                first: None,
+                last: None,
+            }
+        }
+
+        fn record(&mut self, n: u32) {
+            if self.first.is_none() {
+                self.first = Some(n)
+            } else {
+                self.last = Some(n)
+            }
+        }
+
+        fn value(self) -> u32 {
+            self.first.unwrap() * 10 + self.last.unwrap_or(self.first.unwrap())
+        }
+    }
+
+    let out: u32 = input
+        .lines()
+        .map(|line| {
+            line.chars().fold(FirstLast::new(), |mut val, char| {
+                if let Some(digit) = char.to_digit(10) {
+                    val.record(digit)
+                }
+                val
+            })
+        })
+        .map(FirstLast::value)
+        .sum();
+
+    println!("{:?}", out);
+}