3 files changed, 93 insertions, 0 deletions
diff --git a/data/2021/17.txt b/data/2021/17.txt
new file mode 100644
index 0000000..c115821
--- /dev/null
+++ b/data/2021/17.txt
@@ -0,0 +1 @@
+target area: x=179..201, y=-109..-63
diff --git a/src/2021/17/mod.rs b/src/2021/17/mod.rs
new file mode 100644
index 0000000..5343360
--- /dev/null
+++ b/src/2021/17/mod.rs
@@ -0,0 +1,88 @@
+fn fire(
+    mut xv: i64,
+    mut yv: i64,
+    xrange: &std::ops::RangeInclusive<i64>,
+    yrange: &std::ops::RangeInclusive<i64>,
+) -> Option<i64> {
+    let mut xpos = 0;
+    let mut ypos = 0;
+    let mut max_height = 0;
+    loop {
+        if xrange.contains(&xpos) && yrange.contains(&ypos) {
+            return Some(max_height);
+        } else if (xv >= 0 && xpos > *xrange.end())
+            || (xv <= 0 && xpos < *xrange.start())
+            || (ypos < *yrange.start())
+        {
+            return None;
+        }
+
+        xpos += xv;
+        ypos += yv;
+        if ypos > max_height {
+            max_height = ypos;
+        }
+        match xv.cmp(&0) {
+            std::cmp::Ordering::Greater => {
+                xv -= 1;
+            }
+            std::cmp::Ordering::Less => {
+                xv += 1;
+            }
+            _ => {}
+        }
+        yv -= 1;
+    }
+}
+
+pub fn part1() -> anyhow::Result<i64> {
+    let rx = regex::Regex::new(
+        r"target area: x=(-?\d+)..(-?\d+), y=(-?\d+)..(-?\d+)",
+    )
+    .unwrap();
+    let line = data_lines!()?.next().unwrap();
+    let captures = rx.captures(&line).unwrap();
+    let xrange: std::ops::RangeInclusive<i64> =
+        captures[1].parse().unwrap()..=captures[2].parse().unwrap();
+    let yrange: std::ops::RangeInclusive<i64> =
+        captures[3].parse().unwrap()..=captures[4].parse().unwrap();
+
+    let mut max_height = 0;
+    for xv in *xrange.start().min(&0)..=*xrange.end().max(&0) {
+        for yv in *yrange.start().min(&0)
+            ..=yrange.start().abs().max(yrange.end().abs())
+        {
+            if let Some(height) = fire(xv, yv, &xrange, &yrange) {
+                if height > max_height {
+                    max_height = height;
+                }
+            }
+        }
+    }
+    Ok(max_height)
+}
+
+pub fn part2() -> anyhow::Result<i64> {
+    let rx = regex::Regex::new(
+        r"target area: x=(-?\d+)..(-?\d+), y=(-?\d+)..(-?\d+)",
+    )
+    .unwrap();
+    let line = data_lines!()?.next().unwrap();
+    let captures = rx.captures(&line).unwrap();
+    let xrange: std::ops::RangeInclusive<i64> =
+        captures[1].parse().unwrap()..=captures[2].parse().unwrap();
+    let yrange: std::ops::RangeInclusive<i64> =
+        captures[3].parse().unwrap()..=captures[4].parse().unwrap();
+
+    let mut count = 0;
+    for xv in *xrange.start().min(&0)..=*xrange.end().max(&0) {
+        for yv in *yrange.start().min(&0)
+            ..=yrange.start().abs().max(yrange.end().abs())
+        {
+            if fire(xv, yv, &xrange, &yrange).is_some() {
+                count += 1;
+            }
+        }
+    }
+    Ok(count)
+}
diff --git a/src/2021/mod.rs b/src/2021/mod.rs
index e11a0ee..e31d57e 100644
--- a/src/2021/mod.rs
+++ b/src/2021/mod.rs
@@ -30,6 +30,8 @@ mod day14;
 mod day15;
 #[path = "16/mod.rs"]
 mod day16;
+#[path = "17/mod.rs"]
+mod day17;
 // NEXT MOD
 
 pub fn run(day: u8, puzzle: u8) -> anyhow::Result<i64> {
@@ -66,6 +68,8 @@ pub fn run(day: u8, puzzle: u8) -> anyhow::Result<i64> {
         (15, 2) => day15::part2(),
         (16, 1) => day16::part1(),
         (16, 2) => day16::part2(),
+        (17, 1) => day17::part1(),
+        (17, 2) => day17::part2(),
         // NEXT PART
         _ => Err(anyhow::anyhow!("unknown puzzle {}-{}", day, puzzle)),
     }