2015, day 12

Author: alokmenghrajani

Cargo.toml

@@ -8,3 +8,4 @@ regex = "0.2"
 rust-crypto = "^0.2"
 fancy-regex = "0.1.0"
 lazy_static = "0.1.16"
+serde_json = "1.0"

src/main.rs

@@ -8,6 +8,7 @@ mod year_2017;
 extern crate crypto;
 extern crate fancy_regex;
 extern crate regex;
+extern crate serde_json;
 
 #[macro_use]
 extern crate lazy_static;
@@ -41,6 +42,7 @@ fn main() {
         (2015, 9) => year_2015::day09::run(inputs::read(year, day)),
         (2015, 10) => year_2015::day10::run("3113322113"),
         (2015, 11) => year_2015::day11::run("vzbxkghb"),
+        (2015, 12) => year_2015::day12::run(&inputs::read_first_line(year, day)),
         (2015, _) => println!("work in progress..."),
 
         // 2016

src/year_2015/day12.rs

@@ -0,0 +1,44 @@
+use serde_json;
+use serde_json::Value;
+
+pub fn run(input: &[u8]) {
+    let part1 = solve_part1(input);
+    println!("part 1: {}", part1);
+    assert_eq!(part1, 119433);
+
+    let part2 = solve_part2(input);
+    println!("part 2: {}", part2);
+    assert_eq!(part2, 68466);
+}
+
+fn solve_part1(buf: &[u8]) -> i64 {
+    let v: Value = serde_json::from_slice(buf).unwrap();
+
+    return sum(v, true);
+}
+
+fn solve_part2(buf: &[u8]) -> i64 {
+    let v: Value = serde_json::from_slice(buf).unwrap();
+
+    return sum(v, false);
+}
+
+fn sum(v: Value, include_red: bool) -> i64 {
+    return match v {
+        Value::Null => 0,
+        Value::Bool(_) => 0,
+        Value::Number(n) => n.as_i64().unwrap(),
+        Value::String(_) => 0,
+        Value::Array(v) => v.into_iter().map(|e| sum(e, include_red)).sum(),
+        Value::Object(ref v) => {
+            let mut max = 0;
+            for v in v.values() {
+                if (v == "red") && !include_red {
+                    return 0;
+                }
+                max += sum(v.clone(), include_red);
+            }
+            return max;
+        }
+    };
+}

src/year_2015/mod.rs

@@ -9,3 +9,4 @@ pub mod day08;
 pub mod day09;
 pub mod day10;
 pub mod day11;
+pub mod day12;