Day 12 part 1.

src/day12.rs

@@ -0,0 +1,24 @@
+use aoc_runner_derive::aoc;
+use regex::Regex;
+
+#[aoc(day12, part1)]
+fn part1(input: &str) -> i64 {
+    Regex::new(r"-?\d+")
+        .unwrap()
+        .find_iter(input)
+        .map(|m| m.as_str().parse::<i64>().unwrap())
+        .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1("[1,2,3]"), 6);
+        assert_eq!(part1("{\"a\":2,\"b\":4}"), 6);
+        assert_eq!(part1(r"[[[3]]]"), 3);
+        assert_eq!(part1(r#"{"a":{"b":4},"c":-1}"#), 3);
+    }
+}

src/lib.rs

@@ -4,5 +4,6 @@ extern crate aoc_runner_derive;
 
 mod day10;
 mod day11;
+mod day12;
 
 aoc_lib! { year = 2015 }