1 files changed, 71 insertions, 0 deletions
diff --git a/aoc/2024/07/rust/src/main.rs b/aoc/2024/07/rust/src/main.rs
new file mode 100644
index 0000000..df586b1
--- /dev/null
+++ b/aoc/2024/07/rust/src/main.rs
@@ -0,0 +1,71 @@
+use std::io;
+
+fn main() -> io::Result<()> {
+    let eqns = io::stdin()
+        .lines()
+        .flatten()
+        .collect::<Vec<_>>()
+        .iter()
+        .map(|line| line.split_once(": ").unwrap())
+        .map(|(ans, nums)| {
+            (
+                ans.parse::<u64>().unwrap(),
+                nums.split_whitespace()
+                    .map(|s| s.parse::<u64>().unwrap())
+                    .collect::<Vec<_>>(),
+            )
+        })
+        .collect::<Vec<_>>();
+
+    let silver: u64 = eqns.iter().map(crate::silver).sum();
+    let gold: u64 = eqns.iter().map(crate::gold).sum();
+
+    println!("silver: {silver}");
+    println!("gold: {gold}");
+
+    return Ok(());
+}
+
+fn concat(x: &u64, y: &u64) -> u64 {
+    x * (10u64.pow(y.ilog10() + 1)) + y
+}
+
+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
+            }
+        }
+        _ => 0,
+    }
+}