day21 part1

1 files changed, 97 insertions, 0 deletions

diff --git a/src/bin/day21.rs b/src/bin/day21.rs
new file mode 100644
index 0000000..86a7fa1
--- /dev/null
+++ b/src/bin/day21.rs
@@ -0,0 +1,97 @@
+use std::collections::HashMap;
+
+static DAY: u8 = 21;
+
+fn main() {
+    let input = advent::read_lines(DAY);
+    println!("{DAY}a: {}", yelled_number(&input));
+    println!("{DAY}b: {}", 0);
+}
+
+#[derive(PartialEq,Eq,Hash)]
+enum Job {
+    Yell { number: u64 },
+    Add { op1: String, op2: String },
+    Sub { op1: String, op2: String },
+    Mul { op1: String, op2: String },
+    Div { op1: String, op2: String },
+}
+
+impl Job {
+    fn new(input: &str) -> Job {
+        if let Some((op1, op2)) = input.split_once(" + ") {
+            Job::Add { op1: op1.to_string(), op2: op2.to_string() }
+        } else if let Some((op1, op2)) = input.split_once(" - ") {
+            Job::Sub { op1: op1.to_string(), op2: op2.to_string() }
+        } else if let Some((op1, op2)) = input.split_once(" * ") {
+            Job::Mul { op1: op1.to_string(), op2: op2.to_string() }
+        } else if let Some((op1, op2)) = input.split_once(" / ") {
+            Job::Div { op1: op1.to_string(), op2: op2.to_string() }
+        } else {
+            Job::Yell { number: input.parse().unwrap() }
+        }
+    }
+}
+
+#[derive(PartialEq,Eq,Hash)]
+struct Monkey {
+    name: String,
+    job: Job,
+}
+
+impl Monkey {
+    fn new(input: &str) -> Monkey {
+        let (name, job) = input.split_once(": ").unwrap();
+        Monkey {
+            name: name.to_string(),
+            job: Job::new(job),
+        }
+    }
+}
+
+fn calculate_number(monkeys: &HashMap<String,Monkey>, name: &str) -> u64 {
+    let monkey = monkeys.get(name).expect("monkey should be in list");
+    match &monkey.job {
+        Job::Yell { number } => *number,
+        Job::Add { op1, op2 } => calculate_number(monkeys, &op1) + calculate_number(monkeys, &op2),
+        Job::Sub { op1, op2 } => calculate_number(monkeys, &op1) - calculate_number(monkeys, &op2),
+        Job::Mul { op1, op2 } => calculate_number(monkeys, &op1) * calculate_number(monkeys, &op2),
+        Job::Div { op1, op2 } => calculate_number(monkeys, &op1) / calculate_number(monkeys, &op2),
+    }
+}
+
+fn yelled_number(input: &[String]) -> u64 {
+    let monkeys = input.iter()
+                       .map(|x| Monkey::new(x))
+                       .map(|x| (x.name.clone(), x))
+                       .collect::<HashMap<_,_>>();
+    calculate_number(&monkeys, "root")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = [
+            "root: pppw + sjmn",
+            "dbpl: 5",
+            "cczh: sllz + lgvd",
+            "zczc: 2",
+            "ptdq: humn - dvpt",
+            "dvpt: 3",
+            "lfqf: 4",
+            "humn: 5",
+            "ljgn: 2",
+            "sjmn: drzm * dbpl",
+            "sllz: 4",
+            "pppw: cczh / lfqf",
+            "lgvd: ljgn * ptdq",
+            "drzm: hmdt - zczc",
+            "hmdt: 32",
+        ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
+
+        assert_eq!(yelled_number(&input), 152);
+    }
+}