Day 03

diff --git a/src/day03.rs b/src/day03.rs
new file mode 100644 (file)
index 0000000..9be94ea
--- /dev/null
+++ b/src/day03.rs
@@ -0,0 +1,68 @@
+use std::io::BufRead;
+
+use regex::Regex;
+
+pub fn read_program<R>(mut reader: R) -> String
+where
+    R: BufRead,
+{
+    let mut output = String::new();
+    reader.read_to_string(&mut output).unwrap();
+    output
+}
+
+pub fn execute_corrupted_program(prog: &str) -> i32 {
+    let mul_re = Regex::new(r#"mul\((\d{1,3}),(\d{1,3})\)"#).unwrap();
+
+    let mut val = 0;
+    for cap in mul_re.captures_iter(prog) {
+        let n1 = cap[1].parse::<i32>().unwrap();
+        let n2 = cap[2].parse::<i32>().unwrap();
+        val += n1 * n2
+    }
+
+    val
+}
+
+pub fn execute_corrupted_program_dodont(prog: &str) -> i32 {
+    let mul_re = Regex::new(r#"mul\((\d{1,3}),(\d{1,3})\)|don't\(\)|do\(\)"#).unwrap();
+
+    let mut val = 0;
+    let mut enable = true;
+    for cap in mul_re.captures_iter(prog) {
+        match &cap[0] {
+            "don't()" => enable = false,
+            "do()" => enable = true,
+            _ if enable => {
+                let n1 = cap[1].parse::<i32>().unwrap();
+                let n2 = cap[2].parse::<i32>().unwrap();
+                val += n1 * n2
+            }
+            _ => (), // Skip 'mul' instruction.
+        }
+    }
+    val
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    static CORRUPTED_PROGRAM_PART1: &str =
+        r#"xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))"#;
+
+    #[test]
+    fn test_part1() {
+        let v = execute_corrupted_program(CORRUPTED_PROGRAM_PART1);
+        assert_eq!(v, 161);
+    }
+
+    static CORRUPTED_PROGRAM_PART2: &str =
+        r#"xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))"#;
+
+    #[test]
+    fn test_part2() {
+        let v = execute_corrupted_program_dodont(CORRUPTED_PROGRAM_PART2);
+        assert_eq!(v, 48);
+    }
+}

diff --git a/src/days.rs b/src/days.rs
index 03e4e34..1424849 100644 (file)
--- a/src/days.rs
+++ b/src/days.rs
@@ -21,3 +21,13 @@ pub fn day02() -> String {
         day02::nb_of_safe_reports_with_tolerance(&reports)
     )
 }
+
+pub fn day03() -> String {
+    let f = fs::File::open("data/day03.input").unwrap();
+    let program = day03::read_program(BufReader::new(f));
+    format!(
+        "part1: {}, part2: {}",
+        day03::execute_corrupted_program(&program),
+        day03::execute_corrupted_program_dodont(&program)
+    )
+}

diff --git a/src/main.rs b/src/main.rs
index 15bf0ef..51cf7ce 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,7 +5,7 @@ use rayon::prelude::*;
 
 mod day01;
 mod day02;
-// mod day03;
+mod day03;
 // mod day04;
 // mod day05;
 // mod day06;
@@ -45,7 +45,7 @@ fn main() {
     let days: Vec<fn() -> String> = vec![
         days::day01,
         days::day02,
-        // days::day03,
+        days::day03,
         // days::day04,
         // days::day05,
         // days::day06,