diff --git a/Cargo.lock b/Cargo.lock
index e152003..faeb77e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6,11 +6,72 @@ version = 3
 name = "advent_of_code"
 version = "0.9.2"
 dependencies = [
+ "itertools",
  "pico-args",
+ "regex",
 ]
 
+[[package]]
+name = "aho-corasick"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2969dcb958b36655471fc61f7e416fa76033bdd4bfed0678d8fee1e2d07a1f0"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "either"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a26ae43d7bcc3b814de94796a5e736d4029efb0ee900c12e2d54c993ad1a1e07"
+
+[[package]]
+name = "itertools"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "25db6b064527c5d482d0423354fcd07a89a2dfe07b67892e62411946db7f07b0"
+dependencies = [
+ "either",
+]
+
+[[package]]
+name = "memchr"
+version = "2.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
+
 [[package]]
 name = "pico-args"
 version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5be167a7af36ee22fe3115051bc51f6e6c7054c9348e28deb4f49bd6f705a315"
+
+[[package]]
+name = "regex"
+version = "1.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "380b951a9c5e80ddfd6136919eef32310721aa4aacd4889a8d39124b026ab343"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f804c7828047e88b2d32e2d7fe5a105da8ee3264f01902f796c8e067dc2483f"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c08c74e62047bb2de4ff487b251e4a92e24f48745648451635cec7d591162d9f"
diff --git a/Cargo.toml b/Cargo.toml
index ac5c09e..6f8b797 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,4 +14,6 @@ doctest = false
 test_lib = []
 
 [dependencies]
+itertools = "0.12.0"
 pico-args = "0.5.0"
+regex = "1.10.2"
diff --git a/src/bin/01.rs b/src/bin/01.rs
new file mode 100644
index 0000000..1d72aef
--- /dev/null
+++ b/src/bin/01.rs
@@ -0,0 +1,54 @@
+advent_of_code::solution!(1);
+
+use itertools::Itertools;
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let result = input
+        .lines()
+        .map(|line| line.chars().filter(|&c| c.is_numeric()).collect::<String>())
+        .filter(|line| line.len() >= 1)
+        .map(|line| {
+            line.chars().nth(0).unwrap().to_digit(10).unwrap() * 10
+                + line.chars().last().unwrap().to_digit(10).unwrap()
+        })
+        .sum();
+    Some(result)
+}
+
+// list of written out numbers
+const NUMBERS: [&str; 10] = [
+    "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
+];
+
+#[allow(unused_variables)]
+pub fn part_two(input: &str) -> Option<u32> {
+    let res = input
+        .lines()
+        // recursively replace all written out numbers with their digits
+        .map(|line| {
+            let mut line = line.to_string();
+            for (i, number) in NUMBERS.iter().enumerate() {
+                line = line.replace(number, format!("{}{}{}", number, i, number).as_str());
+            }
+            line
+        })
+        .join("\n");
+    part_one(&res)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(142));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_filepath("examples", "01-b"));
+        assert_eq!(result, Some(281));
+    }
+}
diff --git a/src/template/mod.rs b/src/template/mod.rs
index 4403b95..e04faa5 100644
--- a/src/template/mod.rs
+++ b/src/template/mod.rs
@@ -19,6 +19,16 @@ pub fn read_file(folder: &str, day: Day) -> String {
     f.expect("could not open input file")
 }
 
+pub fn read_filepath(folder: &str, filename: &str) -> String {
+    let cwd = env::current_dir().unwrap();
+    let filepath = cwd
+        .join("data")
+        .join(folder)
+        .join(format!("{filename}.txt"));
+    let f = fs::read_to_string(filepath);
+    f.expect("could not open input file")
+}
+
 /// Creates the constant `DAY` and sets up the input and runner for each part.
 #[macro_export]
 macro_rules! solution {