rust 2024 07: refactor

1 files changed, 37 insertions, 21 deletions

diff --git a/2024/07/rust/src/main.rs b/2024/07/rust/src/main.rs
index 07fef57..df586b1 100644
--- a/2024/07/rust/src/main.rs
+++ b/2024/07/rust/src/main.rs
@@ -17,17 +17,8 @@ fn main() -> io::Result<()> {
         })
         .collect::<Vec<_>>();
 
-    let silver: u64 = eqns
-        .iter()
-        .filter(|(ans, nums)| calibration(ans, nums, false))
-        .map(|(ans, _)| ans)
-        .sum();
-
-    let gold: u64 = eqns
-        .iter()
-        .filter(|(ans, nums)| calibration(ans, nums, true))
-        .map(|(ans, _)| ans)
-        .sum();
+    let silver: u64 = eqns.iter().map(crate::silver).sum();
+    let gold: u64 = eqns.iter().map(crate::gold).sum();
 
     println!("silver: {silver}");
     println!("gold: {gold}");
@@ -39,17 +30,42 @@ fn concat(x: &u64, y: &u64) -> u64 {
     x * (10u64.pow(y.ilog10() + 1)) + y
 }
 
-fn calibration(want: &u64, nums: &[u64], gold: bool) -> bool {
-    match nums {
-        [] => unreachable!(),
-        [x] => want == x,
-        [x, y, xs @ ..] => {
-            if x > want {
-                return false;
+fn calibration(want: u64, x: &u64, y: &u64, rest: &[u64], gold: bool) -> bool {
+    if *x > want {
+        return false;
+    }
+    match rest {
+        [] => want == x + y || want == x * y || (gold && want == concat(x, y)),
+        [z, rest @ ..] => {
+            calibration(want, &(x + y), z, rest, gold)
+                || calibration(want, &(x * y), z, rest, gold)
+                || (gold && calibration(want, &concat(x, y), z, rest, gold))
+        }
+    }
+}
+
+fn silver((want, nums): &(u64, Vec<u64>)) -> u64 {
+    match nums.as_slice() {
+        [x, y, rest @ ..] => {
+            if calibration(*want, x, y, rest, false) {
+                *want
+            } else {
+                0
+            }
+        }
+        _ => 0,
+    }
+}
+
+fn gold((want, nums): &(u64, Vec<u64>)) -> u64 {
+    match nums.as_slice() {
+        [x, y, rest @ ..] => {
+            if calibration(*want, x, y, rest, true) {
+                *want
+            } else {
+                0
             }
-            calibration(want, &[&[x + y], xs].concat(), gold) ||
-            calibration(want, &[&[x * y], xs].concat(), gold) ||
-            (gold && calibration(want, &[&[concat(x, y)], xs].concat(), gold) )
         }
+        _ => 0,
     }
 }