From b7db7574faf02505ff151d72606a513d574aebfd Mon Sep 17 00:00:00 2001
From: kageru <kageru@encode.moe>
Date: Wed, 20 Dec 2023 11:27:02 +0100
Subject: [PATCH] add 2023/20/1

---
 2023/inputs/day20     |  58 ++++++++++++++++
 2023/src/bin/day20.rs | 151 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 209 insertions(+)
 create mode 100644 2023/inputs/day20
 create mode 100644 2023/src/bin/day20.rs

diff --git a/2023/inputs/day20 b/2023/inputs/day20
new file mode 100644
index 0000000..53bea22
--- /dev/null
+++ b/2023/inputs/day20
@@ -0,0 +1,58 @@
+%xf -> qr
+%qr -> bt, zt
+%xm -> gp, cq
+%zs -> ct
+&vg -> lg
+%dx -> bt, tz
+%tq -> jm
+%pr -> gp, pf
+&nb -> lg
+%tz -> bt
+%kj -> fk
+%hx -> rb
+%xh -> zs, rb
+&vc -> lg
+%tl -> bn
+%bb -> kf, rb
+%nn -> xf, bt
+%nk -> nn, bt
+%kp -> vk
+&bt -> tl, nk, pb, xf, vg
+%sr -> vs, ml
+%sh -> zk
+%jm -> ml, kp
+%kq -> tl, bt
+%vs -> tq, ml
+%sv -> dx, bt
+%gs -> gp
+%kf -> rb, ph
+%ct -> rt, rb
+%sj -> kj, rb
+%kh -> ml
+%nt -> gs, gp
+%bn -> sv, bt
+%lx -> ff, gp
+%rt -> hq
+%ph -> rb, hx
+&ls -> lg
+%nv -> xm
+%df -> nv
+%vk -> tk
+%cq -> gp, mq
+%hq -> bb
+&lg -> rx
+%zk -> ml, ps
+&ml -> kp, sr, tq, nb, tk, sh, vk
+%pf -> gp, nt
+%ff -> gp, df
+%zt -> pb, bt
+broadcaster -> sj, sr, tp, nk
+%mq -> pr
+&rb -> vc, zs, fk, hq, rt, sj, kj
+%pb -> kq
+%qz -> ml, kh
+%tp -> gp, lx
+%tk -> sh
+&gp -> df, ls, mq, tp, nv
+%fk -> xh
+%ps -> qz, ml
diff --git a/2023/src/bin/day20.rs b/2023/src/bin/day20.rs
new file mode 100644
index 0000000..caaeb47
--- /dev/null
+++ b/2023/src/bin/day20.rs
@@ -0,0 +1,151 @@
+#![feature(test)]
+extern crate test;
+use std::collections::VecDeque;
+
+use self::{Node::*, Pulse::*};
+use aoc2023::{boilerplate, common::*};
+use fnv::FnvHashMap as Map;
+
+const DAY: usize = 20;
+type Parsed<'a> = Map<&'a str, (Node<'a>, Vec<&'a str>)>;
+
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+enum Pulse {
+    High,
+    Low,
+}
+
+#[derive(Debug, Clone)]
+enum Node<'a> {
+    Broadcaster,
+    FlipFlop(bool),
+    Conjunction(Map<&'a str, Pulse>),
+}
+
+fn parse_input(raw: &str) -> Parsed {
+    let mut parsed: Parsed = raw
+        .lines()
+        .map(|line| line.split_once(" -> ").unwrap())
+        .map(|(node, outputs)| {
+            let (node, name) = match node.as_bytes()[0] {
+                b'%' => (FlipFlop(false), &node[1..]),
+                b'&' => (Conjunction(Map::default()), &node[1..]),
+                _ => (Broadcaster, node),
+            };
+            let outputs = outputs.split(", ").collect();
+            (name, (node, outputs))
+        })
+        .collect();
+    // Now the annoying part: set all inputs of all conjunctions to Low
+    let mut con_inputs = Map::<&str, Vec<&str>>::default();
+    for (input, (_, outputs)) in parsed.iter() {
+        for output in outputs {
+            if matches!(parsed.get(output), Some((Conjunction(_), _))) {
+                match con_inputs.get_mut(output) {
+                    Some(v) => v.push(input),
+                    None => {
+                        con_inputs.insert(output, vec![input]);
+                    }
+                };
+            }
+        }
+    }
+    for (con, inputs) in con_inputs {
+        let Some((Conjunction(map), _)) = parsed.get_mut(con) else { unreachable!() };
+        for i in inputs {
+            map.insert(i, Low);
+        }
+    }
+    parsed
+}
+
+const EMPTY: &Vec<&str> = &Vec::new();
+
+fn process<'a, 'b>(map: &'a mut Parsed<'b>, name: &'b str, pulse: Pulse, src: &'b str) -> (&'b str, Pulse, &'a Vec<&'b str>) {
+    // println!("{src} ({pulse:?}) -> {name}");
+    // First modify as needed…
+    match map.get_mut(name) {
+        // nodes that don’t lead anywhere, e.g. `output` from the second example
+        None => return ("", Low, EMPTY),
+        Some((FlipFlop(_), _)) if pulse == High => return ("", Low, EMPTY),
+        Some((FlipFlop(b), _)) => *b = !*b,
+        Some((Conjunction(inputs), _)) => {
+            inputs.insert(src, pulse);
+        }
+        Some(_) => (),
+    };
+    // …then match again on an immutable borrow from the map so we can return the output vector.
+    let (pulse, out) = match (map.get(name).unwrap(), pulse) {
+        ((Broadcaster, out), p) => (p, out),
+        // Careful: we already flipped the flipflops above, so off gives low and on gives high.
+        ((FlipFlop(false), out), Low) => (Low, out),
+        ((FlipFlop(true), out), Low) => (High, out),
+        ((FlipFlop(_), _), High) => (High, EMPTY),
+        ((Conjunction(inputs), out), _) => {
+            if inputs.values().all(|&v| v == High) {
+                (Low, out)
+            } else {
+                (High, out)
+            }
+        }
+    };
+    (name, pulse, out)
+}
+
+fn push_button<'a, 'b>(map: &'a mut Parsed<'b>) -> (usize, usize) {
+    let mut low_count = 1; // initial button
+    let mut high_count = 0;
+    let mut queue = VecDeque::new();
+    queue.push_back(("button", Low, "broadcaster"));
+    while let Some((src, pulse, output)) = queue.pop_front() {
+        let (src, pulse, outputs) = process(map, output, pulse, src);
+        for output in outputs {
+            queue.push_back((src, pulse, output));
+            match pulse {
+                Low => low_count += 1,
+                High => high_count += 1,
+            }
+        }
+    }
+    (low_count, high_count)
+}
+
+fn part1<'a>(map: &Parsed) -> usize {
+    let mut map = map.to_owned();
+    let (mut low, mut high) = (0, 0);
+    for _ in 0..1000 {
+        let (new_low, new_high) = push_button(&mut map);
+        low += new_low;
+        high += new_high;
+    }
+    low * high
+}
+
+fn part2(parsed: &Parsed) -> usize {
+    unimplemented!()
+}
+
+boilerplate! {
+    TEST_INPUT == "\
+broadcaster -> a, b, c
+%a -> b
+%b -> c
+%c -> inv
+&inv -> a",
+    TEST_INPUT_2 == "\
+broadcaster -> a
+%a -> inv, con
+&inv -> b
+%b -> con
+&con -> output"
+    for tests: {
+        part1: {
+            TEST_INPUT => 32000000,
+            TEST_INPUT_2 => 11687500,
+        },
+        part2: { TEST_INPUT => 0 },
+    },
+    bench1 == 929810733,
+    bench2 == 0,
+    bench_parse: Map::len => 58,
+}