From c54e7dbf8a1624867b0f8bfd2e28fdbd481f4588 Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Sun, 10 Dec 2023 11:27:37 +0100
Subject: Add day9

---
 2023/day9/src/lib.rs | 122 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 2023/day9/src/lib.rs

(limited to '2023/day9/src')

diff --git a/2023/day9/src/lib.rs b/2023/day9/src/lib.rs
new file mode 100644
index 0000000..a1b0588
--- /dev/null
+++ b/2023/day9/src/lib.rs
@@ -0,0 +1,122 @@
+pub fn part1(input: &str) -> i32 {
+    let mut res: i32 = 0;
+
+    let m: Vec<Vec<i32>> = input
+        .trim_end()
+        .split('\n')
+        .map(|x| {
+            x.split(' ')
+                .map(|y| y.parse::<i32>().unwrap())
+                .collect::<Vec<i32>>()
+        })
+        .collect();
+
+    for i in m {
+        let mut aux: Vec<Vec<i32>> = vec![i];
+
+        let mut z = 1;
+        loop {
+            aux.push(vec![]);
+            for j in 1..aux[z - 1].len() {
+                let x = aux[z - 1][j] - aux[z - 1][j - 1];
+                aux[z].push(x);
+            }
+
+            if aux[z].iter().filter(|&k| *k != 0).count() == 0 {
+                aux[z].push(0);
+                break;
+            }
+
+            z += 1;
+        }
+
+        let n = aux.len() - 1;
+        for j in (0..n).rev() {
+            let t = aux[j + 1][aux[j + 1].len() - 1];
+            let r = aux[j][aux[j].len() - 1];
+            aux[j].push(t + r);
+        }
+
+        res += aux[0][aux[0].len() - 1];
+    }
+
+    res
+}
+
+pub fn part2(input: &str) -> i32 {
+    let mut res: i32 = 0;
+
+    let m: Vec<Vec<i32>> = input
+        .trim_end()
+        .split('\n')
+        .map(|x| {
+            x.split(' ')
+                .map(|y| y.parse::<i32>().unwrap())
+                .collect::<Vec<i32>>()
+        })
+        .collect();
+
+    for i in m {
+        let mut aux: Vec<Vec<i32>> = vec![i];
+
+        let mut z = 1;
+        loop {
+            aux.push(vec![]);
+            for j in 1..aux[z - 1].len() {
+                let x = aux[z - 1][j] - aux[z - 1][j - 1];
+                aux[z].push(x);
+            }
+
+            if aux[z].iter().filter(|&k| *k != 0).count() == 0 {
+                aux[z].push(0);
+                break;
+            }
+
+            z += 1;
+        }
+
+        let n = aux.len() - 1;
+        for j in (0..n).rev() {
+            let t = aux[j + 1][0];
+            let r = aux[j][0];
+            aux[j].insert(0, r - t);
+        }
+
+        res += aux[0][0];
+    }
+
+    res
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn example_part1() {
+        let input = include_str!("../example.txt");
+        let result = part1(input);
+        assert_eq!(result, 114);
+    }
+
+    #[test]
+    fn input_part1() {
+        let input = include_str!("../input.txt");
+        let result = part1(input);
+        assert_eq!(result, 2008960228);
+    }
+
+    #[test]
+    fn example_part2() {
+        let input = include_str!("../example.txt");
+        let result = part2(input);
+        assert_eq!(result, 2);
+    }
+
+    #[test]
+    fn input_part2() {
+        let input = include_str!("../input.txt");
+        let result = part2(input);
+        assert_eq!(result, 71585);
+    }
+}
-- 
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