From 6efeba31118533d95645f5e8be21af58960e1708 Mon Sep 17 00:00:00 2001
From: Adrian Groh <adrian.groh@t-online.de>
Date: Tue, 24 Dec 2024 10:42:36 +0100
Subject: [PATCH] Add day24 part1

---
 day24/Cargo.lock  |   7 ++++
 day24/Cargo.toml  |   6 +++
 day24/src/main.rs | 105 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+)
 create mode 100644 day24/Cargo.lock
 create mode 100644 day24/Cargo.toml
 create mode 100644 day24/src/main.rs

diff --git a/day24/Cargo.lock b/day24/Cargo.lock
new file mode 100644
index 0000000..6d2ef2f
--- /dev/null
+++ b/day24/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "day24"
+version = "0.1.0"
diff --git a/day24/Cargo.toml b/day24/Cargo.toml
new file mode 100644
index 0000000..ddaaf58
--- /dev/null
+++ b/day24/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "day24"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/day24/src/main.rs b/day24/src/main.rs
new file mode 100644
index 0000000..4827763
--- /dev/null
+++ b/day24/src/main.rs
@@ -0,0 +1,105 @@
+use std::{cmp::Reverse, collections::HashMap};
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+enum Gate {
+    InputGate(bool),
+    CalcGate(CalcGate),
+}
+
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+enum Operation {
+    And,
+    Or,
+    Xor,
+}
+
+impl From<&str> for Operation {
+    fn from(value: &str) -> Self {
+        match value {
+            "AND" => Self::And,
+            "OR" => Self::Or,
+            "XOR" => Self::Xor,
+            _ => panic!(),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+struct CalcGate {
+    operation: Operation,
+    lhs: String,
+    rhs: String,
+}
+
+fn parse(input: &str) -> HashMap<String, Gate> {
+    let mut res = HashMap::new();
+    let (inputs, calcs) = input.split_once("\n\n").unwrap();
+    res.extend(inputs.lines().map(|l| {
+        let (name, val) = l.split_once(": ").unwrap();
+        (name.to_string(), Gate::InputGate(val == "1"))
+    }));
+    res.extend(calcs.lines().map(|l| {
+        let mut iter = l.split(' ');
+        let lhs = iter.next().unwrap();
+        let op = iter.next().unwrap();
+        let rhs = iter.next().unwrap();
+        let name = iter.nth(1).unwrap();
+        (
+            name.to_string(),
+            Gate::CalcGate(CalcGate {
+                operation: Operation::from(op),
+                lhs: lhs.to_string(),
+                rhs: rhs.to_string(),
+            }),
+        )
+    }));
+    res
+}
+
+fn get_gate_value(
+    gate: &str,
+    gates: &HashMap<String, Gate>,
+    cache: &mut HashMap<String, bool>,
+) -> bool {
+    if let Some(v) = cache.get(gate) {
+        return *v;
+    }
+    let res = match gates.get(gate).unwrap() {
+        Gate::InputGate(val) => *val,
+        Gate::CalcGate(calc_gate) => match calc_gate.operation {
+            Operation::And => {
+                get_gate_value(&calc_gate.lhs, gates, cache)
+                    & get_gate_value(&calc_gate.rhs, gates, cache)
+            }
+            Operation::Or => {
+                get_gate_value(&calc_gate.lhs, gates, cache)
+                    | get_gate_value(&calc_gate.rhs, gates, cache)
+            }
+            Operation::Xor => {
+                get_gate_value(&calc_gate.lhs, gates, cache)
+                    ^ get_gate_value(&calc_gate.rhs, gates, cache)
+            }
+        },
+    };
+    cache.insert(gate.to_string(), res);
+    res
+}
+
+fn part1(gates: &HashMap<String, Gate>) -> usize {
+    let mut output_bits: Vec<_> = gates.keys().filter(|g| g.starts_with("z")).collect();
+    let mut cache = HashMap::new();
+    output_bits.sort_unstable_by_key(|v| Reverse(v.to_string()));
+    let mut res: usize = 0;
+    for bit in output_bits {
+        res <<= 1;
+        if get_gate_value(bit, gates, &mut cache) {
+            res += 1;
+        }
+    }
+    res
+}
+
+fn main() {
+    let input = parse(include_str!("../input.txt"));
+    println!("{}", part1(&input));
+}