[TASK] Solved day 9

src/day9.rs

@@ -0,0 +1,69 @@
+use crate::day_solver::DaySolver;
+#[cfg(test)]
+use crate::util::read_file;
+
+pub struct Day9 {
+    histories: Vec<Vec<i32>>
+}
+
+impl Day9 {
+
+    pub fn create(input: String) -> Self {
+        return Day9 {
+            histories: input.lines().map(|h| h.split_whitespace().map(|n| n.parse().unwrap()).collect()).collect()
+        }
+    }
+}
+
+fn find_next_in_history(history: &Vec<i32>) -> i32 {
+
+    if history.iter().all(|n| n == &0) {
+        return 0
+    }
+
+    let mut history_derivative = Vec::with_capacity(history.len());
+    for i in 0..history.len() - 1 {
+        history_derivative.push(history[i + 1] - history[i])
+    }
+
+    return history.last().unwrap() + find_next_in_history(&history_derivative);
+
+}
+
+impl DaySolver for Day9 {
+
+
+    fn solve_part1(&mut self) -> String {
+        return self.histories.iter()
+            .map(|h| {
+                let res = find_next_in_history(h);
+                // println!("{:?} yields {}", h, res);
+                res
+            })
+            .sum::<i32>().to_string()
+    }
+
+    fn solve_part2(&mut self) -> String {
+        return self.histories.iter()
+            .map(|h| {
+                let mut h_reverse = h.clone();
+                h_reverse.reverse();
+                let res = find_next_in_history(&h_reverse);
+                // println!("{:?} yields {}", h, res);
+                res
+            })
+            .sum::<i32>().to_string()
+    }
+}
+
+#[test]
+fn test_part1() {
+    let mut day = Day9::create(read_file("input/day09_example.txt"));
+    assert_eq!("114", day.solve_part1());
+}
+
+#[test]
+fn test_part2() {
+    let mut day = Day9::create(read_file("input/day09_example.txt"));
+    assert_eq!("2", day.solve_part2());
+}