Day 17

src/day17.rs

@@ -0,0 +1,40 @@
+use std::cmp::max;
+use std::ops::RangeInclusive;
+
+pub fn day17() {
+    solve(&(20..=30), &(-10..=-5));
+    solve(&(287..=309), &(-76..=-48));
+}
+
+fn solve(target_x: &RangeInclusive<isize>, target_y: &RangeInclusive<isize>) {
+    let maxes = (0..=*target_x.end()).flat_map(|vx| {
+        (*target_y.start()..=500).filter_map(move |vy| count_steps(vx, vy, target_x, target_y))
+    });
+    dbg!(maxes.clone().max());
+    dbg!(maxes.count());
+}
+
+fn count_steps(
+    mut vx: isize,
+    mut vy: isize,
+    target_x: &RangeInclusive<isize>,
+    target_y: &RangeInclusive<isize>,
+) -> Option<isize> {
+    let mut x = 0;
+    let mut y = 0;
+    let mut max_y = 0;
+    loop {
+        x += vx;
+        y += vy;
+        vx -= vx.signum();
+        vy -= 1;
+        max_y = max(max_y, y);
+        if target_x.contains(&x) && target_y.contains(&y) {
+            return Some(max_y);
+        } else if !target_x.contains(&x) && vx == 0 {
+            return None;
+        } else if !target_y.contains(&y) && y < *target_y.start() {
+            return None;
+        }
+    }
+}

src/main.rs

@@ -15,7 +15,8 @@ mod day13;
 mod day14;
 mod day15;
 mod day16;
+mod day17;
 
 fn main() {
-    day16::day16();
+    day17::day17();
 }