day3 solution 2

1 files changed, 22 insertions, 8 deletions

diff --git a/src/bin/day3.rs b/src/bin/day3.rs
index 02cb385..7acbd3d 100644
--- a/src/bin/day3.rs
+++ b/src/bin/day3.rs
@@ -4,19 +4,28 @@ static DAY: u8 = 3;
 
 fn main() {
     let input = advent::read_lines(DAY);
-    println!("{DAY}a: {}", sum_multiplications(&input));
-    println!("{DAY}b: {}", 0);
+    println!("{DAY}a: {}", sum_multiplications(&input, true));
+    println!("{DAY}b: {}", sum_multiplications(&input, false));
 }
 
-fn sum_multiplications(input: &[String]) -> u32 {
-    let re = Regex::new(r"mul\(([0-9]{1,3}),([0-9]{1,3})\)").unwrap();
+fn sum_multiplications(input: &[String], ignore_do: bool) -> u32 {
+    let re = Regex::new(r"(do)\(\)|(don't)\(\)|(mul)\(([0-9]{1,3}),([0-9]{1,3})\)").unwrap();
 
     let mut sum = 0;
+    let mut muls_enabled = true;
     for line in input {
         for cap in re.captures_iter(line) {
-            let f1 = cap[1].parse::<u32>().unwrap();
-            let f2 = cap[2].parse::<u32>().unwrap();
-            sum += f1 * f2;
+            if cap.get(1).is_some() { // do
+                muls_enabled = true;
+            } else if cap.get(2).is_some() { // don't
+                muls_enabled = false;
+            } else if cap.get(3).is_some() { // mul
+                if ignore_do || muls_enabled {
+                    let f1 = cap[4].parse::<u32>().unwrap();
+                    let f2 = cap[5].parse::<u32>().unwrap();
+                    sum += f1 * f2;
+                }
+            }
         }
     }
     sum
@@ -31,6 +40,11 @@ mod tests {
         let input = [
             "xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))"
         ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
-        assert_eq!(sum_multiplications(&input), 161);
+        assert_eq!(sum_multiplications(&input, true), 161);
+
+        let input = [
+            "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))"
+        ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
+        assert_eq!(sum_multiplications(&input, false), 48);
     }
 }