Day 17 part 2.

src/day17.rs

@@ -7,37 +7,67 @@ fn parse(input: &str) -> Vec<u32> {
 
 #[aoc(day17, part1)]
 fn part1(input: &[u32]) -> usize {
-    bar(input, 150)
+    bar1(input, 150)
 }
 
-fn bar(containers: &[u32], target: u32) -> usize {
-    baz(containers, target, 0)
+fn bar1(containers: &[u32], target: u32) -> usize {
+    baz1(containers, target, 0)
 }
 
-fn baz(containers: &[u32], target: u32, filled: u32) -> usize {
+fn baz1(containers: &[u32], target: u32, filled: u32) -> usize {
     if filled > target {
         return 0;
     } else if filled == target {
         return 1;
-    } else if containers.len() == 0 {
+    } else if containers.is_empty() {
         return 0;
     }
 
-    baz(&containers[1..], target, filled + containers[0])
-        + baz(&containers[1..], target, filled)
+    baz1(&containers[1..], target, filled + containers[0]) + baz1(&containers[1..], target, filled)
+}
+
+fn bar2(containers: &[u32], target: u32) -> usize {
+    let mut counts = vec![0; containers.len() + 1];
+    baz2(containers, target, 0, 0, &mut counts);
+    counts.into_iter().find(|count| *count > 0).unwrap()
+}
+
+fn baz2(containers: &[u32], target: u32, filled: u32, count: usize, counts: &mut [usize]) {
+    if filled > target {
+        return;
+    } else if filled == target {
+        counts[count] += 1;
+        return;
+    } else if containers.is_empty() {
+        return;
+    }
+
+    baz2(
+        &containers[1..],
+        target,
+        filled + containers[0],
+        count + 1,
+        counts,
+    );
+    baz2(&containers[1..], target, filled, count, counts);
 }
 
 #[aoc(day17, part2)]
 fn part2(_input: &[u32]) -> usize {
-    0
+    bar2(_input, 150)
 }
 
 #[cfg(test)]
 mod test {
-    use crate::day17::bar;
+    use crate::day17::{bar1, bar2};
 
     #[test]
     fn part1() {
-        assert_eq!(bar(&[20, 15, 10, 5, 5], 25), 4)
+        assert_eq!(bar1(&[20, 15, 10, 5, 5], 25), 4)
+    }
+
+    #[test]
+    fn part2() {
+        assert_eq!(bar2(&[20, 15, 10, 5, 5], 25), 3)
     }
 }