day9

src/day9.rs

@@ -0,0 +1,73 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use itertools::Itertools;
+
+const PREAMBLE_LEN: usize = 25;
+
+#[aoc_generator(day9)]
+fn parse(input: &str) -> Vec<u64> {
+    input.lines().map(str::parse).map(Result::unwrap).collect_vec()
+}
+
+#[aoc(day9, part1)]
+fn part1(input: &Vec<u64>) -> u64 {
+    for i in PREAMBLE_LEN..input.len() {
+        if let None = input[i - PREAMBLE_LEN..i]
+        .iter()
+        .combinations(2)
+        .find(|x| x.iter().cloned().sum::<u64>() == input[i]) {
+            return input[i];
+        }
+    }
+    unreachable!()
+}
+
+#[aoc(day9, part2)]
+fn part2(input: &Vec<u64>) -> u64 {
+    let to_find = part1(input);
+
+    for len in 2..input.len() {
+        if let Some(nums) = input
+        .windows(len)
+        .find(|x| x.iter().cloned().sum::<u64>() == to_find) {
+            return nums.iter().min().unwrap() + nums.iter().max().unwrap();
+        }
+    }
+    unreachable!()
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+const EX: &str = r"35
+20
+15
+25
+47
+40
+62
+55
+65
+95
+102
+117
+150
+182
+127
+219
+299
+277
+309
+576";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&parse(EX)), 127);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&parse(EX)), 62);
+    }
+}

src/lib.rs

@@ -1,3 +1,4 @@
+mod day9;
 mod day8;
 mod day7;
 mod day6;