Day 12 part 2.

Cargo.lock

@@ -8,6 +8,7 @@ version = "0.1.0"
 dependencies = [
  "aoc-runner",
  "aoc-runner-derive",
+ "json",
  "regex",
 ]
 
@@ -55,6 +56,12 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1306f3464951f30e30d12373d31c79fbd52d236e5e896fd92f96ec7babbbe60b"
 
+[[package]]
+name = "json"
+version = "0.12.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "078e285eafdfb6c4b434e0d31e8cfcb5115b651496faca5749b88fafd4f23bfd"
+
 [[package]]
 name = "memchr"
 version = "2.7.1"

Cargo.toml

@@ -11,3 +11,4 @@ bench = false
 aoc-runner = "0.3.0"
 aoc-runner-derive = "0.3.0"
 regex = "1.10.2"
+json = "0.12.4"

src/day12.rs

@@ -1,4 +1,5 @@
 use aoc_runner_derive::aoc;
+use json::{parse, JsonValue};
 use regex::Regex;
 
 #[aoc(day12, part1)]
@@ -10,6 +11,32 @@ fn part1(input: &str) -> i64 {
         .sum()
 }
 
+#[aoc(day12, part2)]
+fn part2(input: &str) -> i64 {
+    let json = parse(input).unwrap();
+    sum(&json)
+}
+
+fn sum(json: &JsonValue) -> i64 {
+    match json {
+        JsonValue::Null => 0,
+        JsonValue::Short(_) => 0,
+        JsonValue::String(_) => 0,
+        JsonValue::Number(_) => json.as_i64().unwrap(),
+        JsonValue::Boolean(_) => 0,
+        JsonValue::Object(o) => {
+            if o.iter().any(|(_, value)| {
+                value.is_string() && Some("red") == value.as_str()
+            }) {
+                0
+            } else {
+                o.iter().map(|(_key, value)| sum(value)).sum()
+            }
+        }
+        JsonValue::Array(a) => a.iter().map(|e| sum(e)).sum(),
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;