diff --git a/Cargo.lock b/Cargo.lock
index e0b5f84..87ad879 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,17 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "ahash"
+version = "0.7.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "891477e0c6a8957309ee5c45a6368af3ae14bb510732d2684ffa19af310920f9"
+dependencies = [
+ "getrandom",
+ "once_cell",
+ "version_check",
+]
+
 [[package]]
 name = "ahash"
 version = "0.8.12"
@@ -72,6 +83,7 @@ dependencies = [
  "indicatif",
  "itertools",
  "lazy_static",
+ "memoize",
  "misc",
  "nom",
  "rayon",
@@ -113,10 +125,10 @@ version = "0.54.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9718806c4a2fe9e8a56fd736f97b340dd10ed1be8ed733ed50449f351dc33cae"
 dependencies = [
- "ahash",
+ "ahash 0.8.12",
  "cached_proc_macro",
  "cached_proc_macro_types",
- "hashbrown",
+ "hashbrown 0.14.5",
  "once_cell",
  "thiserror",
  "web-time",
@@ -247,17 +259,37 @@ version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
 
+[[package]]
+name = "getrandom"
+version = "0.2.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "335ff9f135e4384c8150d6f27c6daed433577f86b4750418338c01a1a2528592"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 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"
+dependencies = [
+ "ahash 0.7.8",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.14.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e5274423e17b7c9fc20b6e7e208532f9b19825d82dfd615708b70edd83df41f1"
 dependencies = [
- "ahash",
+ "ahash 0.8.12",
  "allocator-api2",
 ]
 
@@ -318,12 +350,44 @@ version = "0.2.177"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2874a2af47a2325c2001a6e6fad9b16a53b802102b528163885171cf92b15976"
 
+[[package]]
+name = "lru"
+version = "0.7.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e999beba7b6e8345721bd280141ed958096a2e4abdf74f67ff4ce49b4b54e47a"
+dependencies = [
+ "hashbrown 0.12.3",
+]
+
 [[package]]
 name = "memchr"
 version = "2.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f52b00d39961fc5b2736ea853c9cc86238e165017a493d1d5c8eac6bdc4cc273"
 
+[[package]]
+name = "memoize"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8d1d5792299bab3f8b5d88d1b7a7cb50ad7ef039a8c4d45a6b84880a6526276"
+dependencies = [
+ "lazy_static",
+ "lru",
+ "memoize-inner",
+]
+
+[[package]]
+name = "memoize-inner"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6dd8f89255d8ff313afabed9a3c83ef0993cc056679dfd001f5111a026f876f7"
+dependencies = [
+ "lazy_static",
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
@@ -576,6 +640,12 @@ version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[package]]
+name = "wasi"
+version = "0.11.1+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ccf3ec651a847eb01de73ccad15eb7d99f80485de043efb2f370cd654f4ea44b"
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.106"
diff --git a/Cargo.toml b/Cargo.toml
index 9609600..f3cc600 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,7 @@ grid = {version = "0.1.0", path = "utils/grid"}
 indicatif = { version = "0.17.9", features = ["rayon"] }
 itertools = "0.13.0"
 lazy_static = "1.5.0"
+memoize = "0.5.1"
 misc = {path = "utils/misc"}
 nom = "7.1.3"
 rayon = "1.10.0"
diff --git a/src/day3.rs b/src/day3.rs
index f3a8c64..5cf2ada 100644
--- a/src/day3.rs
+++ b/src/day3.rs
@@ -1,36 +1,52 @@
-use aoc_runner_derive::{aoc, aoc_generator};
+use std::collections::HashMap;
 
-type Bank = Vec<u8>;
+use aoc_runner_derive::{aoc, aoc_generator};
+use lazy_static::lazy_static;
+use memoize::memoize;
+
+type Bank = [u8];
 
 #[aoc_generator(day3)]
-fn parse(input: &str) -> Vec<Bank> {
+fn parse(input: &str) -> Vec<Vec<u8>> {
     input
         .lines()
         .map(|bank| bank.bytes().map(|c| c - b'0').collect())
         .collect()
 }
 
-fn max_joltage(bank: &Bank, n: usize) -> u64 {
-    assert_eq!(n, 2, "unimplemented");
-    let mut max = 0;
-    for start in 0..bank.len() - 1 {
-        let cur = bank[start] as u64 * 10u64.pow(n as u32 - 1)
-            + *bank[start + 1..].iter().max().unwrap() as u64;
-        if cur > max {
-            max = cur
-        }
+#[memoize]
+fn max_joltage(bank: Vec<u8>, n: usize) -> u64 {
+    if n == 1 {
+        return *bank.iter().max().unwrap() as u64;
     }
-    max
+
+    (0..bank.len() - n + 1)
+        .map(|start| {
+            bank[start] as u64 * 10u64.pow(n as u32 - 1)
+                + max_joltage(bank[start + 1..].to_vec(), n - 1)
+        })
+        .max()
+        .unwrap()
+
+    // let mut max = 0;
+    // for start in 0..bank.len() - n + 1 {
+    //     let cur = bank[start] as u64 * 10u64.pow(n as u32 - 1)
+    //         + *bank[start + 1..].iter().max().unwrap() as u64;
+    //     if cur > max {
+    //         max = cur
+    //     }
+    // }
+    // max
 }
 
 #[aoc(day3, part1)]
-fn part1(input: &Vec<Bank>) -> u64 {
-    input.iter().map(|bank| max_joltage(bank, 2)).sum()
+fn part1(input: &Vec<Vec<u8>>) -> u64 {
+    input.iter().map(|bank| max_joltage(bank.clone(), 2)).sum()
 }
 
 #[aoc(day3, part2)]
-fn part2(input: &Vec<Bank>) -> u64 {
-    todo!()
+fn part2(input: &Vec<Vec<u8>>) -> u64 {
+    input.iter().map(|bank| max_joltage(bank.clone(), 12)).sum()
 }
 
 #[cfg(test)]
@@ -49,6 +65,6 @@ mod tests {
 
     #[test]
     fn part2_example() {
-        assert_eq!(part2(&parse(EXAMPLE)), 0);
+        assert_eq!(part2(&parse(EXAMPLE)), 3121910778619);
     }
 }