diff --git a/Cargo.lock b/Cargo.lock
index dc466c3..cf0d25f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8,7 +8,7 @@ version = "0.8.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5a15f179cd60c4584b8a8c596927aadc462e27f2ca70c04e0071964a73ba7a75"
 dependencies = [
- "cfg-if",
+ "cfg-if 1.0.4",
  "once_cell",
  "version_check",
  "zerocopy",
@@ -72,15 +72,34 @@ dependencies = [
  "rayon",
  "regex",
  "rstest",
+ "rustc_data_structures",
  "wide",
 ]
 
+[[package]]
+name = "arrayvec"
+version = "0.7.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c02d123df017efcdfbd739ef81735b36c5ba83ec3c59c80a9d7ecc718f92e50"
+
 [[package]]
 name = "autocfg"
 version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"
 
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
+[[package]]
+name = "bitflags"
+version = "2.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "812e12b5285cc515a9c72a5c1d3b6d46a19dac5acfef5265968c166106e31dd3"
+
 [[package]]
 name = "bumpalo"
 version = "3.19.0"
@@ -126,6 +145,12 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ade8366b8bd5ba243f0a58f036cc0ca8a2f069cff1a2351ef1cac6b083e16fc0"
 
+[[package]]
+name = "cfg-if"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
 [[package]]
 name = "cfg-if"
 version = "1.0.4"
@@ -211,6 +236,15 @@ version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
 
+[[package]]
+name = "ena"
+version = "0.14.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d248bdd43ce613d87415282f69b9bb99d947d290b10962dd6c56233312c2ad5"
+dependencies = [
+ "log",
+]
+
 [[package]]
 name = "encode_unicode"
 version = "1.0.0"
@@ -223,6 +257,22 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "877a4ace8713b0bcf2a4e7eec82529c029f1d0619886d18145fea96c3ffe5c0f"
 
+[[package]]
+name = "errno"
+version = "0.3.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
+dependencies = [
+ "libc",
+ "windows-sys",
+]
+
+[[package]]
+name = "fastrand"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37909eebbb50d72f9059c3b6d82c0463f2ff062c9e95845c43a6c9c0355411be"
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -278,6 +328,18 @@ dependencies = [
  "slab",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "899def5c37c4fd7b2664648c28120ecec138e4d395b459e5ca34f9cce2dd77fd"
+dependencies = [
+ "cfg-if 1.0.4",
+ "libc",
+ "r-efi",
+ "wasip2",
+]
+
 [[package]]
 name = "glob"
 version = "0.3.3"
@@ -288,6 +350,12 @@ checksum = "0cc23270f6e1808e30a928bdc84dea0b9b4136a8bc82338574f23baf47bbd280"
 name = "grid"
 version = "0.1.0"
 
+[[package]]
+name = "hashbrown"
+version = "0.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8a9ee70c43aaf417c914396645a0fa852624801b24ebb7ae78fe8272889ac888"
+
 [[package]]
 name = "hashbrown"
 version = "0.15.5"
@@ -305,12 +373,29 @@ version = "0.16.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
 
+[[package]]
+name = "hermit-abi"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fc0fef456e4baa96da950455cd02c081ca953b141298e41db3fc7e36b1da849c"
+
 [[package]]
 name = "ident_case"
 version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b9e0384b61958566e926dc50660321d12159025e767c18e043daf26b70104c39"
 
+[[package]]
+name = "indexmap"
+version = "1.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bd070e393353796e801d209ad339e89596eb4c8d430d18ede6a1cced8fafbd99"
+dependencies = [
+ "autocfg",
+ "hashbrown 0.12.3",
+ "rustc-rayon 0.5.1",
+]
+
 [[package]]
 name = "indexmap"
 version = "2.12.1"
@@ -359,6 +444,16 @@ version = "1.0.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4a5f13b858c8d314ee3e8f639011f7ccefe71f97f96e50151fb991f267928e2c"
 
+[[package]]
+name = "jobserver"
+version = "0.1.34"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9afb3de4395d6b3e67a780b6de64b51c978ecf11cb9a462c66be7d4ca9039d33"
+dependencies = [
+ "getrandom",
+ "libc",
+]
+
 [[package]]
 name = "js-sys"
 version = "0.3.83"
@@ -369,18 +464,54 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "lazy_static"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
+
 [[package]]
 name = "libc"
 version = "0.2.178"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "37c93d8daa9d8a012fd8ab92f088405fb202ea0b6ab73ee2482ae66af4f42091"
 
+[[package]]
+name = "linux-raw-sys"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df1d3c3b53da64cf5760482273a98e575c651a67eec7f77df96b5b642de8f039"
+
+[[package]]
+name = "lock_api"
+version = "0.4.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "224399e74b87b5f3557511d98dff8b14089b3dadafcab6bb93eab67d3aace965"
+dependencies = [
+ "scopeguard",
+]
+
+[[package]]
+name = "log"
+version = "0.4.29"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5e5032e24019045c762d3c0f28f5b6b8bbf38563a65908389bf7978758920897"
+
 [[package]]
 name = "memchr"
 version = "2.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f52b00d39961fc5b2736ea853c9cc86238e165017a493d1d5c8eac6bdc4cc273"
 
+[[package]]
+name = "memmap2"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "723e3ebdcdc5c023db1df315364573789f8857c11b631a2fdfad7c00f5c046b4"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "memoffset"
 version = "0.9.1"
@@ -407,12 +538,45 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "num_cpus"
+version = "1.17.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "91df4bbde75afed763b708b7eee1e8e7651e02d97f6d5dd763e89367e957b23b"
+dependencies = [
+ "hermit-abi",
+ "libc",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.21.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 
+[[package]]
+name = "parking_lot"
+version = "0.12.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93857453250e3077bd71ff98b6a65ea6621a19bb0f559a85248955ac12c45a1a"
+dependencies = [
+ "lock_api",
+ "parking_lot_core",
+]
+
+[[package]]
+name = "parking_lot_core"
+version = "0.9.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2621685985a2ebf1c516881c026032ac7deafcda1a2c9b7850dc81e3dfcb64c1"
+dependencies = [
+ "cfg-if 1.0.4",
+ "libc",
+ "redox_syscall",
+ "smallvec",
+ "windows-link",
+]
+
 [[package]]
 name = "pin-project-lite"
 version = "0.2.16"
@@ -458,6 +622,12 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "r-efi"
+version = "5.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
+
 [[package]]
 name = "rayon"
 version = "1.11.0"
@@ -478,6 +648,15 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "redox_syscall"
+version = "0.5.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed2bf2547551a7053d6fdfafda3f938979645c44812fbfcda098faae3f1a362d"
+dependencies = [
+ "bitflags 2.10.0",
+]
+
 [[package]]
 name = "regex"
 version = "1.12.2"
@@ -530,7 +709,7 @@ version = "0.26.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c845311f0ff7951c5506121a9ad75aec44d083c31583b2ea5a30bcb0b0abba0"
 dependencies = [
- "cfg-if",
+ "cfg-if 1.0.4",
  "glob",
  "proc-macro-crate",
  "proc-macro2",
@@ -542,6 +721,79 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "rustc-hash"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08d43f7aa6b08d49f382cde6a7982047c3426db949b1424bc4b7ec9ae12c6ce2"
+
+[[package]]
+name = "rustc-rayon"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9974ab223660e61c1b4e7b43b827379df286736ca988308ce7e16f59f2d89246"
+dependencies = [
+ "crossbeam-deque",
+ "either",
+ "rustc-rayon-core 0.3.2",
+]
+
+[[package]]
+name = "rustc-rayon"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2cd9fb077db982d7ceb42a90471e5a69a990b58f71e06f0d8340bb2cf35eb751"
+dependencies = [
+ "either",
+ "rustc-rayon-core 0.5.1",
+]
+
+[[package]]
+name = "rustc-rayon-core"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "564bfd27be8db888d0fa76aa4335e7851aaed0c2c11ad1e93aeb9349f6b88500"
+dependencies = [
+ "crossbeam-deque",
+ "crossbeam-utils",
+ "lazy_static",
+ "num_cpus",
+]
+
+[[package]]
+name = "rustc-rayon-core"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f42932dcd3bcbe484b38a3ccf79b7906fac41c02d408b5b1bac26da3416efdb"
+dependencies = [
+ "crossbeam-deque",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "rustc_data_structures"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a38bae9c6afa27015bcaa2869e03bb111ecf0d0e0edc2da559a91d4057174c9a"
+dependencies = [
+ "arrayvec",
+ "bitflags 1.3.2",
+ "cfg-if 0.1.10",
+ "ena",
+ "indexmap 1.9.3",
+ "jobserver",
+ "libc",
+ "memmap2",
+ "parking_lot",
+ "rustc-hash",
+ "rustc-rayon 0.3.2",
+ "rustc-rayon-core 0.3.2",
+ "stable_deref_trait",
+ "tempfile",
+ "tracing",
+ "winapi",
+]
+
 [[package]]
 name = "rustc_version"
 version = "0.4.1"
@@ -551,6 +803,19 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rustix"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd15f8a2c5551a84d56efdc1cd049089e409ac19a3072d5037a17fd70719ff3e"
+dependencies = [
+ "bitflags 2.10.0",
+ "errno",
+ "libc",
+ "linux-raw-sys",
+ "windows-sys",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.22"
@@ -572,6 +837,12 @@ dependencies = [
  "bytemuck",
 ]
 
+[[package]]
+name = "scopeguard"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
+
 [[package]]
 name = "semver"
 version = "1.0.27"
@@ -626,6 +897,18 @@ version = "0.4.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7a2ae44ef20feb57a68b23d846850f861394c2e02dc425a50098ae8c90267589"
 
+[[package]]
+name = "smallvec"
+version = "1.15.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67b1b7a3b5fe4f1376887184045fcf45c69e92af734b7aaddc05fb777b6fbd03"
+
+[[package]]
+name = "stable_deref_trait"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ce2be8dc25455e1f91df71bfa12ad37d7af1092ae736f3a6cd0e37bc7810596"
+
 [[package]]
 name = "strsim"
 version = "0.11.1"
@@ -654,6 +937,19 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "tempfile"
+version = "3.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d31c77bdf42a745371d260a26ca7163f1e0924b64afa0b688e61b5a9fa02f16"
+dependencies = [
+ "fastrand",
+ "getrandom",
+ "once_cell",
+ "rustix",
+ "windows-sys",
+]
+
 [[package]]
 name = "thiserror"
 version = "2.0.17"
@@ -689,7 +985,7 @@ version = "0.23.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5d7cbc3b4b49633d57a0509303158ca50de80ae32c265093b24c414705807832"
 dependencies = [
- "indexmap",
+ "indexmap 2.12.1",
  "toml_datetime",
  "toml_parser",
  "winnow",
@@ -704,6 +1000,37 @@ dependencies = [
  "winnow",
 ]
 
+[[package]]
+name = "tracing"
+version = "0.1.43"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d15d90a0b5c19378952d479dc858407149d7bb45a14de0142f6c534b16fc647"
+dependencies = [
+ "pin-project-lite",
+ "tracing-attributes",
+ "tracing-core",
+]
+
+[[package]]
+name = "tracing-attributes"
+version = "0.1.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7490cfa5ec963746568740651ac6781f701c9c5ea257c58e057f3ba8cf69e8da"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.111",
+]
+
+[[package]]
+name = "tracing-core"
+version = "0.1.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a04e24fab5c89c6a36eb8558c9656f30d81de51dfa4d3b45f26b21d61fa0a6c"
+dependencies = [
+ "once_cell",
+]
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.22"
@@ -728,13 +1055,22 @@ version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[package]]
+name = "wasip2"
+version = "1.0.1+wasi-0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0562428422c63773dad2c345a1882263bbf4d65cf3f42e90921f787ef5ad58e7"
+dependencies = [
+ "wit-bindgen",
+]
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.106"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0d759f433fa64a2d763d1340820e46e111a7a5ab75f993d1852d70b03dbb80fd"
 dependencies = [
- "cfg-if",
+ "cfg-if 1.0.4",
  "once_cell",
  "rustversion",
  "wasm-bindgen-macro",
@@ -793,6 +1129,28 @@ dependencies = [
  "safe_arch",
 ]
 
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
 [[package]]
 name = "windows-link"
 version = "0.2.1"
@@ -817,6 +1175,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "wit-bindgen"
+version = "0.46.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f17a85883d4e6d00e8a97c586de764dabcc06133f7f1d55dce5cdc070ad7fe59"
+
 [[package]]
 name = "zerocopy"
 version = "0.8.31"
diff --git a/Cargo.toml b/Cargo.toml
index c34d956..b82ea82 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,7 @@ misc = {path = "utils/misc"}
 rayon = "1.11.0"
 regex = "1.11.1"
 rstest = "0.26.1"
+rustc_data_structures = "0.1.2"
 wide = "1.0.2"
 
 [profile.release]
diff --git a/src/day11.rs b/src/day11.rs
index 013edb8..4cb87bb 100644
--- a/src/day11.rs
+++ b/src/day11.rs
@@ -1,11 +1,11 @@
 use aoc_runner_derive::{aoc, aoc_generator};
-use std::collections::{HashMap, HashSet};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 
-type Edges = HashMap<String, Vec<String>>;
+type Edges = FxHashMap<String, Vec<String>>;
 
 #[aoc_generator(day11)]
 fn parse(input: &str) -> Edges {
-    let mut edges: Edges = HashMap::new();
+    let mut edges: Edges = FxHashMap::default();
     for l in input.lines() {
         let (k, rest) = l.split_once(": ").unwrap();
         for v in rest.split_ascii_whitespace() {
@@ -30,8 +30,8 @@ fn find_path(cur: &str, goal: &str, edges: &Edges) -> u64 {
 fn mark_paths<'a>(
     cur: &'a str,
     edges: &'a Edges,
-    mut reachable: HashSet<&'a str>,
-) -> HashSet<&'a str> {
+    mut reachable: FxHashSet<&'a str>,
+) -> FxHashSet<&'a str> {
     reachable.insert(cur);
     if let Some(nexts) = edges.get(cur) {
         for n in nexts {
@@ -43,12 +43,55 @@ fn mark_paths<'a>(
     reachable
 }
 
-#[aoc(day11, part1)]
+fn count_paths_impl<'a>(
+    cur: &'a str,
+    goal: &str,
+    edges: &'a Edges,
+    memo: &mut FxHashMap<&'a str, u64>,
+) -> u64 {
+    if cur == goal {
+        return 1;
+    }
+    if let Some(v) = memo.get(cur) {
+        return *v;
+    }
+
+    if let Some(nexts) = edges.get(cur) {
+        let ret = nexts
+            .iter()
+            .map(|n| count_paths_impl(n, goal, edges, memo))
+            .sum();
+        memo.insert(cur, ret);
+        ret
+    } else {
+        memo.insert(cur, 0);
+        0
+    }
+}
+
+fn count_paths(cur: &str, goal: &str, edges: &Edges) -> u64 {
+    let mut cache = FxHashMap::default();
+    count_paths_impl(cur, goal, edges, &mut cache)
+}
+
+#[aoc(day11, part1, NaiveDfs)]
 fn part1(fwd: &Edges) -> u64 {
     find_path("you", "out", fwd)
 }
 
-#[aoc(day11, part2)]
+#[aoc(day11, part1, MemoDfs)]
+fn part1_memo(fwd: &Edges) -> u64 {
+    count_paths("you", "out", fwd)
+}
+
+#[aoc(day11, part2, MemoDfs)]
+fn part2_memo(edges: &Edges) -> u64 {
+    count_paths("svr", "fft", edges)
+        * count_paths("fft", "dac", edges)
+        * count_paths("dac", "out", edges)
+}
+
+#[aoc(day11, part2, NaiveDfs)]
 fn part2(edges: &Edges) -> u64 {
     let mut rev = Edges::from_iter(edges.keys().map(|k| (k.to_owned(), vec![])));
     for (from, tos) in edges {
@@ -56,17 +99,17 @@ fn part2(edges: &Edges) -> u64 {
             rev.entry(to.to_owned()).or_default().push(from.to_owned());
         }
     }
-    let mut reachable_dac = mark_paths("dac", edges, HashSet::new());
+    let mut reachable_dac = mark_paths("dac", edges, FxHashSet::default());
     reachable_dac = mark_paths("dac", &rev, reachable_dac);
-    let mut reachable_fft = mark_paths("fft", edges, HashSet::new());
+    let mut reachable_fft = mark_paths("fft", edges, FxHashSet::default());
     reachable_fft = mark_paths("fft", &rev, reachable_fft);
 
-    let reachable: HashSet<&str> = reachable_dac
+    let reachable: FxHashSet<&str> = reachable_dac
         .intersection(&reachable_fft)
         .copied()
         .collect();
 
-    let unreachable: HashSet<&str> = HashSet::from_iter(edges.keys().map(|k| k.as_str()))
+    let unreachable: FxHashSet<&str> = FxHashSet::from_iter(edges.keys().map(|k| k.as_str()))
         .difference(&reachable)
         .copied()
         .collect();
@@ -84,14 +127,17 @@ fn part2(edges: &Edges) -> u64 {
         }
     }
 
-    // This is a bit of a cheat from viewing the graph and realizing all paths are ordered this way.
-    // However, knowing that fact that we can partition in this way, we could use a shortest-path algo
-    // to determine which order fft and dac are in.
-    //
-    // The assumption holds on my data and the example, so I think it's probably true of all inputs.
+    // A real graph structure would probably notice that the graphs get split here
+    let mut reachable_edges_excl_fft = reachable_edges.clone();
+    reachable_edges_excl_fft.remove("fft");
+    let mut reachable_edges_excl_dac = reachable_edges.clone();
+    reachable_edges_excl_dac.remove("dac");
+
     find_path("svr", "fft", &reachable_edges)
-        * find_path("fft", "dac", &reachable_edges)
-        * find_path("dac", "out", &reachable_edges)
+        // only svr->fft->dac->out paths appear in my input and in the example, but include the dac->fft ordering
+        // as well, for posterity. It ~doubles runtime.
+        * (find_path("fft", "dac", &reachable_edges) + find_path("dac", "fft", &reachable_edges))
+        * (find_path("dac", "out", &reachable_edges_excl_fft) + find_path("fft", "out", &reachable_edges_excl_dac))
 }
 
 #[cfg(test)]
@@ -131,9 +177,21 @@ hhh: out";
         assert_eq!(part1(&parse(input)), expected);
     }
 
+    #[rstest]
+    #[case(EXAMPLE, 5)]
+    fn part1_memo_example(#[case] input: &str, #[case] expected: u64) {
+        assert_eq!(part1_memo(&parse(input)), expected);
+    }
+
     #[rstest]
     #[case(EXAMPLE2, 2)]
     fn part2_example(#[case] input: &str, #[case] expected: u64) {
         assert_eq!(part2(&parse(input)), expected);
     }
+
+    #[rstest]
+    #[case(EXAMPLE2, 2)]
+    fn part2_memo_example(#[case] input: &str, #[case] expected: u64) {
+        assert_eq!(part2_memo(&parse(input)), expected);
+    }
 }