From e13d0225bccfcae164e3a069db9f5ce62490cdbb Mon Sep 17 00:00:00 2001
From: Sijmen Schoon <me@sijmenschoon.nl>
Date: Tue, 15 Dec 2020 22:28:25 +0100
Subject: [PATCH] Rust: do a day 9

---
 rust/src/main.rs | 61 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 56 insertions(+), 5 deletions(-)

diff --git a/rust/src/main.rs b/rust/src/main.rs
index 32aadf4..726019e 100644
--- a/rust/src/main.rs
+++ b/rust/src/main.rs
@@ -378,10 +378,61 @@ mod day08 {
 }
 
 mod day09 {
-    use std::time::Duration;
+    use std::time::{Duration, Instant};
 
-    pub fn run(_: bool) -> Duration {
-        Duration::new(0, 0)
+    fn part1(numbers: &[usize]) -> usize {
+        for (i, &n) in numbers.iter().enumerate().skip(COUNT) {
+            let mut found = false;
+            for x in i - COUNT..i {
+                for y in x + 1..i {
+                    if numbers[x] + numbers[y] == n {
+                        found = true;
+                    }
+                }
+            }
+
+            if !found {
+                return n;
+            }
+        }
+
+        panic!();
+    }
+
+    fn part2(numbers: &[usize], part1: usize) -> usize {
+        let mut lower = 0;
+        let mut upper = 0;
+        let mut sum = 0;
+
+        while sum != part1 {
+            while sum < part1 {
+                sum += numbers[upper];
+                upper += 1;
+            }
+
+            while sum > part1 {
+                sum -= numbers[lower];
+                lower += 1;
+            }
+        }
+
+        numbers[lower..upper].iter().min().unwrap() + numbers[lower..upper].iter().max().unwrap()
+    }
+
+    const COUNT: usize = 25;
+    pub fn run(print: bool) -> Duration {
+        let input = std::fs::read_to_string("../inputs/09").unwrap();
+        let instant = Instant::now();
+
+        let numbers: Vec<usize> = input.split('\n').flat_map(str::parse).collect();
+        let part1 = part1(&numbers);
+        let part2 = part2(&numbers, part1);
+
+        if print {
+            dbg!(part1, part2);
+        }
+
+        instant.elapsed()
     }
 }
 
@@ -495,7 +546,7 @@ fn main() {
         for day in 0..days.len() {
             let first_run = days[day](false);
             if first_run.as_nanos() == 0 {
-                println!("Day {:>2}: skipped", day);
+                println!("Day {:>2}: skipped", day + 1);
                 continue;
             }
 
@@ -510,7 +561,7 @@ fn main() {
             total += elapsed;
         }
 
-        println!("-------------------");
+        println!("--------------------");
         println!("Total:  {:?}", total);
     }
 }