day3: part 2, add memoize

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);
     }
 }