From 838b1f7661e9b29e0cc226892fbb7f4c561398a7 Mon Sep 17 00:00:00 2001
From: Joseph Chamochumbi <sephxd1234@gmail.com>
Date: Fri, 17 Dec 2021 08:21:34 +0100
Subject: [PATCH] feat: Solution Day 17, :star: :star2: w/ Rust and TypeScript

---
 2021/day-17/Cargo.toml  |   9 ++++
 2021/day-17/src/main.rs |  92 +++++++++++++++++++++++++++++++++++
 2021/deno/day-17.ts     | 103 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 204 insertions(+)
 create mode 100644 2021/day-17/Cargo.toml
 create mode 100644 2021/day-17/src/main.rs
 create mode 100644 2021/deno/day-17.ts

diff --git a/2021/day-17/Cargo.toml b/2021/day-17/Cargo.toml
new file mode 100644
index 0000000..806ac37
--- /dev/null
+++ b/2021/day-17/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+authors = ["Joseph Chamochumbi <sephxd1234@gmail.com>"]
+edition = "2018"
+name = "day-17"
+version = "0.1.0"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[dependencies]
+aoc = {git = "https://github.com/icyJoseph/advent-of-code.git"}
diff --git a/2021/day-17/src/main.rs b/2021/day-17/src/main.rs
new file mode 100644
index 0000000..57e1afe
--- /dev/null
+++ b/2021/day-17/src/main.rs
@@ -0,0 +1,92 @@
+use aoc;
+
+fn solve(raw: String) -> () {
+    let spec = raw
+        .trim()
+        .replace("target area: ", "")
+        .split(", ")
+        .map(|entry| {
+            let coord = entry.split("=").collect::<Vec<&str>>()[1];
+            let ranges = coord
+                .split("..")
+                .map(|n| parse_num::<isize>(n))
+                .collect::<Vec<isize>>();
+            ranges
+        })
+        .collect::<Vec<Vec<isize>>>();
+
+    let lower_y = spec[1][0];
+
+    let initial_dy = lower_y.abs() - 1;
+
+    let max_y = initial_dy * (initial_dy + 1) / 2;
+
+    println!("Part One: {:?}", max_y);
+
+    let lower_x = spec[0][0];
+
+    let upper_x = spec[0][1];
+    let upper_y = spec[1][1];
+
+    let min_dx = {
+        let mut value = 0;
+
+        loop {
+            if value * (value + 1) > 2 * lower_x {
+                break;
+            }
+            value += 1;
+        }
+
+        value
+    };
+
+    use std::collections::HashSet;
+
+    let mut initial: HashSet<(isize, isize)> = HashSet::new();
+
+    let x_range = lower_x..=upper_x;
+    let y_range = lower_y..=upper_y;
+
+    for dx in min_dx..=upper_x {
+        for dy in lower_y..=lower_y.abs() {
+            let mut velocity = [dx, dy];
+            let mut position = [0, 0];
+
+            loop {
+                if x_range.contains(&position[0]) && y_range.contains(&position[1]) {
+                    initial.insert((dx, dy));
+                }
+
+                if velocity[0] == 0 {
+                    if !x_range.contains(&position[0]) {
+                        break;
+                    }
+                }
+
+                if position[1] < lower_y && velocity[1] < 0 {
+                    break;
+                }
+
+                position = [position[0] + velocity[0], position[1] + velocity[1]];
+
+                velocity = [velocity[0] - velocity[0].signum(), velocity[1] - 1];
+            }
+        }
+    }
+    println!("Part Two: {:?}", initial.len());
+}
+
+fn main() {
+    let input = aoc::get_input(2021, 17);
+
+    solve(input);
+}
+
+// Utilities
+fn parse_num<T: std::str::FromStr>(str: &str) -> T {
+    match str.trim().parse::<T>() {
+        Ok(n) => n,
+        _ => panic!("Error parsing"),
+    }
+}
diff --git a/2021/deno/day-17.ts b/2021/deno/day-17.ts
new file mode 100644
index 0000000..c5ccd13
--- /dev/null
+++ b/2021/deno/day-17.ts
@@ -0,0 +1,103 @@
+const input = await Deno.readTextFile("./input/day-17.in");
+// const input = await Deno.readTextFile("./input/example.in");
+
+const target = input
+  .replace("target area: ", "")
+  .split(", ")
+  .map((range) => range.split("=")[1].split("..").map(Number));
+
+const [xRange, yRange] = target;
+
+type Position = { x: number; y: number };
+type Velocity = { dx: number; dy: number };
+
+const updatePosition = (position: Position, velocity: Velocity): Position => {
+  return {
+    x: position.x + velocity.dx,
+    y: position.y + velocity.dy
+  };
+};
+
+const updateVelocity = (velocity: Velocity): Velocity => {
+  // drag effect
+  const dx = velocity.dx - Math.sign(velocity.dx);
+  // gravity
+  const dy = velocity.dy - 1;
+  return { dx, dy };
+};
+
+const inRange = (range: number[], coord: number) => {
+  return coord >= range[0] && coord <= range[1];
+};
+
+const inTargetArea = (
+  xRange: number[],
+  yRange: number[],
+  position: Position
+) => {
+  const inYArea = position.y >= yRange[0] && position.y <= yRange[1];
+  const inXArea = position.x >= xRange[0] && position.x <= xRange[1];
+
+  return inYArea && inXArea;
+};
+
+let minDx = 0;
+
+while (1) {
+  if ((minDx * (minDx + 1)) / 2 > xRange[0]) {
+    break;
+  }
+  minDx = minDx + 1;
+}
+
+const maxDx = xRange[1];
+
+const initialDy = Math.abs(yRange[0]) - 1;
+
+const maxY = (initialDy * (initialDy + 1)) / 2;
+
+/**
+ * Part One
+ */
+console.log("Part One:", maxY);
+
+/**
+ * Part Two
+ */
+
+const initial: Set<string> = new Set();
+
+for (let dx = minDx; dx <= maxDx; dx++) {
+  for (let dy = yRange[0]; dy <= -yRange[0]; dy++) {
+    const init = `${dx}.${dy}`;
+    let velocity = { dx, dy };
+    let position = { x: 0, y: 0 };
+
+    while (1) {
+      if (inTargetArea(xRange, yRange, position)) {
+        initial.add(init);
+
+        break;
+      }
+
+      if (
+        (velocity.dx === 0 && position.x < xRange[0]) ||
+        position.x > xRange[1]
+      ) {
+        // falling down out of the target
+        break;
+      }
+
+      if (position.y < yRange[0] && velocity.dy < 0) {
+        // falling down out of the target
+        break;
+      }
+
+      position = updatePosition(position, velocity);
+      // update speed
+      velocity = updateVelocity(velocity);
+    }
+  }
+}
+
+console.log("Part Two:", initial.size);