Solution in Rust

src/main.rs

@@ -0,0 +1,53 @@
+use anyhow::Result;
+use fancy_regex::Regex;
+use std::{
+    collections::HashMap,
+    fs::File,
+    io::{BufRead, BufReader},
+};
+
+fn main() -> Result<()> {
+    let input = File::open("input.txt")?;
+    let reader = BufReader::new(input);
+
+    let patterns = Regex::new(
+        r#"on(?=e)|tw(?=o)|thre(?=e)|four|fiv(?=e)|six|seve(?=n)|eigh(?=t)|nin(?=e)|1|2|3|4|5|6|7|8|9"#,
+    )?;
+    let num_values = HashMap::from([
+        ("on", "1"),
+        ("tw", "2"),
+        ("thre", "3"),
+        ("four", "4"),
+        ("fiv", "5"),
+        ("six", "6"),
+        ("seve", "7"),
+        ("eigh", "8"),
+        ("nin", "9"),
+    ]);
+
+    let mut sum = 0;
+    for line in reader.lines() {
+        let line = line?;
+        let mut nums = vec![];
+        for m in patterns.find_iter(&line) {
+            let m = m?;
+            let text = m.as_str();
+
+            let v: &str = match num_values.get(text) {
+                Some(digit) => digit,
+                None => text,
+            };
+
+            nums.push(v);
+        }
+        let mut value = String::new();
+        value.push_str(nums.first().unwrap());
+        value.push_str(nums.last().unwrap());
+
+        sum += value.parse::<i32>().unwrap();
+    }
+
+    println!("{sum}");
+
+    Ok(())
+}