1 files changed, 120 insertions, 0 deletions
diff --git a/2020/src/bin/day_9.rs b/2020/src/bin/day_9.rs
new file mode 100644
index 0000000..b5a02e6
--- /dev/null
+++ b/2020/src/bin/day_9.rs
@@ -0,0 +1,120 @@
+use bevy::{app::AppExit, prelude::*};
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+fn main() {
+    App::build()
+        .add_resource(WindowDescriptor {
+            title: "Advent of Code".to_string(),
+            width: 1920,
+            height: 1080,
+            ..Default::default()
+        })
+        .add_resource(ClearColor(Color::rgb(0., 0., 0.)))
+        .add_startup_system(setup_camera.system())
+        .add_startup_system(read_input_file.system())
+        .add_stage("add")
+        .add_system_to_stage("add", check_next_num.system())
+        .add_stage("remove")
+        .add_system_to_stage("remove", remove_oldest_line.system())
+        .add_stage("find_range")
+        .add_system_to_stage("find_range", find_contiguous_range.system())
+        .add_plugins(DefaultPlugins)
+        .run();
+}
+
+fn setup_camera(mut commands: Commands) {
+    commands.spawn(Camera2dComponents::default());
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord)]
+struct LineNum(usize);
+#[derive(Clone)]
+struct Num(i64);
+struct Active;
+struct Invalid;
+struct Done;
+
+fn read_input_file(mut commands: Commands) {
+    let f = File::open("./inputs/day_9.txt").unwrap();
+
+    for (line_num, line) in BufReader::new(f).lines().enumerate() {
+        let line = line.unwrap();
+        let line = line.trim();
+        let num = line.parse().unwrap();
+        commands.spawn((LineNum(line_num), Num(num)));
+        if line_num < 25 {
+            commands.with(Active);
+        }
+    }
+}
+
+fn check_next_num(
+    mut commands: Commands,
+    active: Query<With<Active, &Num>>,
+    next: Query<Without<Done, Without<Active, (Entity, &LineNum, &Num)>>>,
+) {
+    if let Some((min_entity, line, num)) = next.iter().min_by_key(|(_, line, _)| line.0) {
+        let mut is_sum = false;
+        for active_1 in active.iter() {
+            for active_2 in active.iter() {
+                is_sum = is_sum || (num.0 == active_1.0 + active_2.0)
+            }
+        }
+        commands.insert_one(min_entity, Active);
+
+        if !is_sum {
+            commands.insert_one(min_entity, Invalid);
+            println!(
+                "{} on line {} was not a sum of the previous lot!",
+                num.0, line.0
+            );
+        }
+    }
+}
+
+fn remove_oldest_line(
+    mut commands: Commands,
+    line_nums: Query<Without<Done, With<Active, (Entity, &LineNum)>>>,
+) {
+    if let Some((min_entity, _)) = line_nums.iter().min_by_key(|(_, line)| line.0) {
+        commands.remove_one::<Active>(min_entity);
+        commands.insert_one(min_entity, Done);
+    } else {
+        println!("All numbers cleared");
+    }
+}
+
+fn find_contiguous_range(
+    mut exit_events: ResMut<Events<AppExit>>,
+    line_nums: Query<(&LineNum, &Num)>,
+    invalid: Query<With<Invalid, &Num>>,
+) {
+    for invalid in invalid.iter() {
+        let mut nums: Vec<(LineNum, Num)> = line_nums
+            .iter()
+            .map(|(line, num)| (line.clone(), num.clone()))
+            .collect();
+
+        nums.sort_by_key(|(line, _num)| line.clone());
+        let nums: Vec<i64> = nums.into_iter().map(|(_line, num)| num.0).collect();
+
+        for min in 0..nums.len() {
+            for max in min + 2..nums.len() + 1 {
+                let sum: i64 = nums[min..max].iter().sum();
+                if sum == invalid.0 {
+                    let min_in_range = nums[min..max].iter().min().unwrap();
+                    let max_in_range = nums[min..max].iter().max().unwrap();
+                    println!(
+                        "Range found! {} + {} = {}",
+                        min_in_range,
+                        max_in_range,
+                        min_in_range + max_in_range
+                    );
+                }
+            }
+        }
+
+        exit_events.send(AppExit);
+    }
+}