From a2b40666189c55ea428379825a1f88eb86407654 Mon Sep 17 00:00:00 2001
From: LongHairedHacker <sebastian@sebastians-site.de>
Date: Fri, 17 Dec 2021 13:58:03 +0100
Subject: [PATCH] Added solution for day 17

---
 inputs/day17.txt  |   1 +
 inputs/sample.txt |   2 +-
 src/bin/day17.rs  | 106 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+), 1 deletion(-)
 create mode 100644 inputs/day17.txt
 create mode 100644 src/bin/day17.rs

diff --git a/inputs/day17.txt b/inputs/day17.txt
new file mode 100644
index 0000000..2fd0935
--- /dev/null
+++ b/inputs/day17.txt
@@ -0,0 +1 @@
+target area: x=209..238, y=-86..-59
diff --git a/inputs/sample.txt b/inputs/sample.txt
index 0d2cbff..a07e02d 100644
--- a/inputs/sample.txt
+++ b/inputs/sample.txt
@@ -1 +1 @@
-8A004A801A8002F478
+target area: x=20..30, y=-10..-5
diff --git a/src/bin/day17.rs b/src/bin/day17.rs
new file mode 100644
index 0000000..f8cac26
--- /dev/null
+++ b/src/bin/day17.rs
@@ -0,0 +1,106 @@
+use std::cmp::Ordering;
+use std::collections::BinaryHeap;
+use std::collections::HashMap;
+use std::collections::HashSet;
+use std::error::Error;
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::vec::Vec;
+
+#[macro_use]
+extern crate lazy_static;
+extern crate regex;
+
+use regex::Regex;
+
+fn is_hit(
+    mut vx: i64,
+    mut vy: i64,
+    target_min_x: i64,
+    target_max_x: i64,
+    target_min_y: i64,
+    target_max_y: i64,
+) -> (bool, i64) {
+    let mut x: i64 = 0;
+    let mut y: i64 = 0;
+
+    let mut max_y = y;
+
+    while x < target_max_x && y > target_min_y {
+        x += vx;
+        y += vy;
+
+        if y > max_y {
+            max_y = y;
+        }
+
+        if vx != 0 {
+            vx -= 1;
+        }
+        vy -= 1;
+
+        if x >= target_min_x && x <= target_max_x && y >= target_min_y && y <= target_max_y {
+            return (true, max_y);
+        }
+    }
+
+    (false, 0)
+}
+
+fn parse_line(line: &str) -> (i64, i64, i64, i64) {
+    lazy_static! {
+        static ref LINE_RE: Regex =
+            Regex::new(r"^target area: x=([0-9]+)\.\.([0-9]+), y=(-[0-9]+)\.\.(-[0-9]+)$").unwrap();
+    }
+
+    let cap = LINE_RE.captures_iter(&line).nth(0).unwrap();
+
+    (
+        cap[1].parse::<i64>().unwrap(),
+        cap[2].parse::<i64>().unwrap(),
+        cap[3].parse::<i64>().unwrap(),
+        cap[4].parse::<i64>().unwrap(),
+    )
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let file = File::open("inputs/day17.txt")?;
+    let line: String = io::BufReader::new(file).lines().next().unwrap()?;
+
+    let target = parse_line(&line);
+
+    let mut max_y = 0;
+    let mut max_velocities = (0, 0);
+
+    for vx in 0..256 {
+        for vy in 0..246 {
+            let (hit, local_max_y) = is_hit(vx, vy, target.0, target.1, target.2, target.3);
+            if hit {
+                println!("Hit {} {}: {}", vx, vy, max_y);
+                if local_max_y > max_y {
+                    max_y = local_max_y;
+                    max_velocities = (vx, vy);
+                }
+            }
+        }
+    }
+
+    println!("Velocities: {},{}", max_velocities.0, max_velocities.1);
+    println!("Answer1: {}", max_y);
+
+    let mut hits = 0;
+
+    for vx in -256..256 {
+        for vy in -256..246 {
+            let (hit, local_max_y) = is_hit(vx, vy, target.0, target.1, target.2, target.3);
+            if hit {
+                println!("Hit {} {}: {}", vx, vy, local_max_y);
+                hits += 1;
+            }
+        }
+    }
+
+    println!("Answer2: {}", hits);
+
+    Ok(())
+}