1 files changed, 75 insertions, 0 deletions
diff --git a/02/src/main.rs b/02/src/main.rs
new file mode 100644
index 0000000..5bcf2c1
--- /dev/null
+++ b/02/src/main.rs
@@ -0,0 +1,75 @@
+use advent_lib::prelude::*;
+
+use regex::Regex;
+use std::convert::TryInto;
+
+
+fn main() -> Result<()> {
+  let mut args = std::env::args();
+  if args.len() != 2 {
+    eprintln!("Usage: advent input");
+  }
+  let _ = args.next();
+  let filename = args.next().unwrap();
+
+  let input = advent_lib::read_lines_file(&filename)?;
+
+  let regex = Regex::new(r"^(\d+)-(\d+) ([a-z]): ([a-z]*)$").unwrap();
+
+  let mut valid_passwords = 0;
+
+  for line in &input {
+    let captures = regex.captures(line).unwrap();
+    let min = captures[1].parse::<i64>()?;
+    let max = captures[2].parse::<i64>()?;
+    let required_char = captures[3].chars().nth(0);
+    let password = &captures[4];
+
+    let mut occurrences = 0;
+    for c in password.chars() {
+      if Some(c) == required_char {
+        occurrences += 1;
+      }
+    }
+
+    if occurrences >= min && occurrences <= max {
+      valid_passwords += 1;
+    }
+  }
+
+  println!("{}", valid_passwords);
+
+  let mut valid_passwords_2 = 0;
+
+  for line in &input {
+    let captures = regex.captures(line).unwrap();
+    let index_a = captures[1].parse::<i64>()?;
+    let index_b = captures[2].parse::<i64>()?;
+    let required_char = captures[3].chars().nth(0);
+    let password = &captures[4];
+
+    let a_is_match =
+            password.len() >= index_a.try_into().unwrap()
+            && required_char
+               == password.chars().nth((index_a - 1).try_into().unwrap());
+    let b_is_match =
+            password.len() >= index_b.try_into().unwrap()
+            && required_char
+               == password.chars().nth((index_b - 1).try_into().unwrap());
+    let mut occurrences = 0;
+    if a_is_match {
+      occurrences += 1;
+    }
+    if b_is_match {
+      occurrences += 1;
+    }
+
+    if occurrences == 1 {
+      valid_passwords_2 += 1;
+    }
+  }
+
+  println!("{}", valid_passwords_2);
+
+  Ok(())
+}