1 files changed, 106 insertions, 0 deletions
diff --git a/src/bin/2021/day17.rs b/src/bin/2021/day17.rs
new file mode 100644
index 0000000..54ee4bb
--- /dev/null
+++ b/src/bin/2021/day17.rs
@@ -0,0 +1,106 @@
+use advent_of_code::prelude::*;
+
+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) {
+            Ordering::Greater => {
+                xv -= 1;
+            }
+            Ordering::Less => {
+                xv += 1;
+            }
+            _ => {}
+        }
+        yv -= 1;
+    }
+}
+
+pub fn parse(
+    fh: File,
+) -> Result<(std::ops::RangeInclusive<i64>, std::ops::RangeInclusive<i64>)> {
+    let line = parse::raw_lines(fh).next().unwrap();
+    let captures = regex_captures!(
+        r"target area: x=(-?\d+)..(-?\d+), y=(-?\d+)..(-?\d+)",
+        &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();
+    Ok((xrange, yrange))
+}
+
+pub fn part1(
+    (xrange, yrange): (
+        std::ops::RangeInclusive<i64>,
+        std::ops::RangeInclusive<i64>,
+    ),
+) -> Result<i64> {
+    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(
+    (xrange, yrange): (
+        std::ops::RangeInclusive<i64>,
+        std::ops::RangeInclusive<i64>,
+    ),
+) -> Result<u64> {
+    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)
+}
+
+#[test]
+fn test() {
+    assert_eq!(
+        part1(parse(parse::data(2021, 17).unwrap()).unwrap()).unwrap(),
+        5886
+    );
+    assert_eq!(
+        part2(parse(parse::data(2021, 17).unwrap()).unwrap()).unwrap(),
+        1806
+    );
+}