1 files changed, 74 insertions, 0 deletions
diff --git a/src/bin/day12.rs b/src/bin/day12.rs
new file mode 100644
index 0000000..35da4fe
--- /dev/null
+++ b/src/bin/day12.rs
@@ -0,0 +1,74 @@
+use json::JsonValue;
+
+fn main() {
+    let input = &advent::read_file(12);
+    println!("12a: {}", sum_numbers(input));
+    println!("12b: {}", sum_numbers_red(input));
+}
+
+fn sum_numbers(input: &str) -> isize {
+    let json = json::parse(input).unwrap();
+    sum_numbers_json(&json, false)
+}
+
+fn sum_numbers_red(input: &str) -> isize {
+    let json = json::parse(input).unwrap();
+    sum_numbers_json(&json, true)
+}
+
+fn contains_red(object: &JsonValue) -> bool {
+    if !object.is_object() {
+        return false;
+    }
+    object.entries().any(|(_, val)| val == "red")
+}
+
+fn sum_numbers_json(input: &JsonValue, ignore_red: bool) -> isize {
+    let mut sum = 0;
+
+    match input {
+        JsonValue::Number(_) => sum += input.as_isize().unwrap(),
+        JsonValue::Object(_) => {
+            if !(ignore_red && contains_red(input)) {
+                for (_, entry) in input.entries() {
+                    sum += sum_numbers_json(entry, ignore_red);
+                }
+            }
+        },
+        JsonValue::Array(_) => {
+            for member in input.members() {
+                sum += sum_numbers_json(member, ignore_red);
+            }
+        },
+        JsonValue::String(_) => {},
+        JsonValue::Short(_) => {},
+        _ => unimplemented!(),
+    }
+
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        assert_eq!(sum_numbers("[1,2,3]"), 6);
+        assert_eq!(sum_numbers(r#"{"a":2,"b":4}"#), 6);
+        assert_eq!(sum_numbers(r#"[[[3]]]"#), 3);
+        assert_eq!(sum_numbers(r#"{"a":{"b":4},"c":-1}"#), 3);
+        assert_eq!(sum_numbers(r#"{"a":[-1,1]}"#), 0);
+        assert_eq!(sum_numbers(r#"[-1,{"a":1}]"#), 0);
+        assert_eq!(sum_numbers("[]"), 0);
+        assert_eq!(sum_numbers("{}"), 0);
+    }
+
+    #[test]
+    fn test_red() {
+        assert_eq!(sum_numbers_red("[1,2,3]"), 6);
+        assert_eq!(sum_numbers_red(r#"[1,{"c":"red","b":2},3]"#), 4);
+        assert_eq!(sum_numbers_red(r#"{"d":"red","e":[1,2,3,4],"f":5}"#), 0);
+        assert_eq!(sum_numbers_red(r#"[1,"red",5]"#), 6);
+    }
+}