Completed day 10. Not wildly happy with my runtime

day_09/cheating.py

@@ -0,0 +1,12 @@
+l = [[int(i) for i in s.split()] for s in open('input.txt').read().split('\n') if s.strip()]
+
+def n(l):
+	if sum(i != 0 for i in l) == 0:
+		return 0
+	m = []
+	for i in range(len(l)-1):
+		m.append(l[i+1]-l[i])
+	return l[-1] + n(m)
+
+print([n(i) for i in l])
+print(sum(n(i[::-1]) for i in l))

day_09/src/lib.rs

@@ -24,7 +24,7 @@ fn expand(sequence: Vec<i64>) -> Array2<i64> {
 }
 
 fn extrapolate(mut reduced: Array2<i64>) -> i64 {
-    let first_i = reduced.outer_iter().position(|row| {row.sum() == 0}).unwrap() - 1;
+    let first_i = reduced.outer_iter().position(|row| {row.iter().all(|x| { x == &0 })}).unwrap() - 1;
     let mut j = reduced.slice(s!(first_i,..)).iter().position(|value| {value == &0}).unwrap();
     for i in (0..=first_i).rev() {
         reduced[[i,j]] = reduced[[i, j-1]] + reduced[[i+1, j-1]];
@@ -37,15 +37,20 @@ pub fn part1(input: &str) -> String {
     input.lines().map(|line| {
         parse_line(line).unwrap().1
     }).map(|x| {
-        dbg!(&x);
         let reduced = expand(x);
-        dbg!(extrapolate(reduced.clone()));
         extrapolate(reduced)
     }).sum::<i64>().to_string()
 }
 
 pub fn part2(input: &str) -> String {
-    todo!()
+    input.lines().map(|line| {
+        let mut nums = parse_line(line).unwrap().1;
+        nums.reverse();
+        nums
+    }).map(|x| {
+        let reduced = expand(x);
+        extrapolate(reduced)
+    }).sum::<i64>().to_string()
 }
 
 pub mod prelude {

day_09/src/main.rs

@@ -16,13 +16,13 @@ mod tests {
 1 3 6 10 15 21
 10 13 16 21 30 45";
         assert_eq!(part1(test_input), "114".to_string());
-        panic!();
     }
 
     #[test]
     fn test_part2() {
-        let test_input = "";
-        assert_eq!(part2(test_input), "".to_string());
+        assert_eq!(part2("0 3 6 9 12 15"), "-3".to_string());
+        assert_eq!(part2("1 3 6 10 15 21"), "0".to_string());
+        assert_eq!(part2("10 13 16 21 30 45"), "5".to_string());
     }
 
 }