day 9 part 2

src/main.rs

@@ -30,7 +30,7 @@ fn main() -> Result<()> {
         }
         let mut prediction = 0;
         for seq in sequences.iter().rev() {
-            prediction += seq.last().unwrap();
+            prediction = seq.first().unwrap() - prediction;
         }
         println!("{prediction}");
         sum += prediction;