From a8291375ba599562a219a9e39effb5c8edbbae5d Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Thu, 15 Dec 2022 09:50:27 +0100
Subject: [PATCH] [rs] Solve 2022_15 part 1

---
 inputs/2022/2022_15.input    | 19 +++++++++++++
 inputs/2022/2022_15.solution |  2 ++
 rs/src/main.rs               |  1 +
 rs/src/y2022.rs              |  1 +
 rs/src/y2022/d15.rs          | 52 ++++++++++++++++++++++++++++++++++++
 5 files changed, 75 insertions(+)
 create mode 100644 inputs/2022/2022_15.input
 create mode 100644 inputs/2022/2022_15.solution
 create mode 100644 rs/src/y2022/d15.rs

diff --git a/inputs/2022/2022_15.input b/inputs/2022/2022_15.input
new file mode 100644
index 0000000..7121b8c
--- /dev/null
+++ b/inputs/2022/2022_15.input
@@ -0,0 +1,19 @@
+Sensor at x=3482210, y=422224: closest beacon is at x=2273934, y=-202439
+Sensor at x=3679395, y=2737332: closest beacon is at x=4104213, y=2980736
+Sensor at x=3173475, y=3948494: closest beacon is at x=3494250, y=3554521
+Sensor at x=27235, y=3642190: closest beacon is at x=-190885, y=3635525
+Sensor at x=3851721, y=1754784: closest beacon is at x=3145586, y=2167751
+Sensor at x=327074, y=3250656: closest beacon is at x=-190885, y=3635525
+Sensor at x=3499970, y=3186179: closest beacon is at x=3494250, y=3554521
+Sensor at x=150736, y=2522778: closest beacon is at x=-85806, y=2000000
+Sensor at x=3000768, y=3333983: closest beacon is at x=2564067, y=3163630
+Sensor at x=1751302, y=1660540: closest beacon is at x=3145586, y=2167751
+Sensor at x=2591068, y=2923079: closest beacon is at x=2564067, y=3163630
+Sensor at x=48946, y=3999178: closest beacon is at x=-190885, y=3635525
+Sensor at x=3695475, y=3863101: closest beacon is at x=3494250, y=3554521
+Sensor at x=1504031, y=2760: closest beacon is at x=2273934, y=-202439
+Sensor at x=3021186, y=2667125: closest beacon is at x=3145586, y=2167751
+Sensor at x=1514629, y=3771171: closest beacon is at x=2564067, y=3163630
+Sensor at x=234064, y=616106: closest beacon is at x=-85806, y=2000000
+Sensor at x=3990843, y=3393575: closest beacon is at x=4104213, y=2980736
+Sensor at x=768875, y=2665271: closest beacon is at x=-85806, y=2000000
diff --git a/inputs/2022/2022_15.solution b/inputs/2022/2022_15.solution
new file mode 100644
index 0000000..d6820f8
--- /dev/null
+++ b/inputs/2022/2022_15.solution
@@ -0,0 +1,2 @@
+Part 1: 4811413
+Part 2: ???
diff --git a/rs/src/main.rs b/rs/src/main.rs
index 0158154..86bbc61 100644
--- a/rs/src/main.rs
+++ b/rs/src/main.rs
@@ -65,6 +65,7 @@ days! {
     Y2022D12: "2022_12" => y2022::d12::solve,
     Y2022D13: "2022_13" => y2022::d13::solve,
     Y2022D14: "2022_14" => y2022::d14::solve,
+    Y2022D15: "2022_15" => y2022::d15::solve,
 }
 
 #[derive(Parser)]
diff --git a/rs/src/y2022.rs b/rs/src/y2022.rs
index 92ca5c0..0871281 100644
--- a/rs/src/y2022.rs
+++ b/rs/src/y2022.rs
@@ -12,3 +12,4 @@ pub mod d11;
 pub mod d12;
 pub mod d13;
 pub mod d14;
+pub mod d15;
diff --git a/rs/src/y2022/d15.rs b/rs/src/y2022/d15.rs
new file mode 100644
index 0000000..aecab4b
--- /dev/null
+++ b/rs/src/y2022/d15.rs
@@ -0,0 +1,52 @@
+use std::collections::HashSet;
+
+struct Sensor {
+    pos: (i32, i32),
+    beac: (i32, i32),
+    dist: i32,
+}
+
+fn parse_coord(coord: &str) -> i32 {
+    let coord = coord.replace(|c| "xy=,:".contains(c), "");
+    coord.parse().unwrap()
+}
+
+pub fn solve(input: String) {
+    let sensors = input
+        .lines()
+        .map(|l| {
+            let parts = l.split_whitespace().collect::<Vec<_>>();
+            let pos = (parse_coord(parts[2]), parse_coord(parts[3]));
+            let beac = (parse_coord(parts[8]), parse_coord(parts[9]));
+            let dist = (pos.0 - beac.0).abs() + (pos.1 - beac.1).abs();
+            Sensor { pos, beac, dist }
+        })
+        .collect::<Vec<_>>();
+
+    // A beacon exactly dist away has 1 field, i. e. x±0
+    // A beacon exactly dist-1 away has 3 fields, i. e. x±1
+    // ...
+    // A beacon exactly 0 away has 2dist+1 fields, i. e. x±dist
+    //
+    // Formula: Go from x-(dist-dy) to x+(dist-dy)
+    let line_at_y = 2000000;
+    let mut part1 = HashSet::new();
+    for (i, sensor) in sensors.iter().enumerate() {
+        eprintln!("Sensor {}", i + 1);
+        let dy = (line_at_y - sensor.pos.1).abs();
+        if dy > sensor.dist {
+            continue;
+        }
+
+        let dx = sensor.dist - dy;
+        for x in (sensor.pos.0 - dx)..=(sensor.pos.0 + dx) {
+            part1.insert(x);
+        }
+    }
+    for sensor in &sensors {
+        if sensor.beac.1 == line_at_y {
+            part1.remove(&sensor.beac.0);
+        }
+    }
+    println!("Part 1: {}", part1.len());
+}