2022_09: rust solution(part 2)

2022/day_9/rust/src/main.rs

@@ -5,10 +5,10 @@ use rope::{parse_series_of_motions, Rope};
 fn main() {
 	let input = include_str!("../../input.txt");
 
-	let mut rope = Rope::new();
+	let mut rope = Rope::new(10, (0, 0));
 	let motions = parse_series_of_motions(input);
 
 	motions.iter().for_each(|motion| rope.apply_motion(motion));
 
-	assert_eq!(rope.get_tails_visited_positions(), 5710);
+	assert_eq!(rope.get_tails_visited_positions(), 2259);
 }

2022/day_9/rust/src/rope.rs

@@ -1,6 +1,7 @@
 use std::{
 	cmp::{max, min},
 	collections::HashSet,
+	ops::Range,
 };
 
 #[derive(Debug, Clone, Copy)]
@@ -42,72 +43,105 @@ pub fn parse_series_of_motions(string: &str) -> Vec<Motion> {
 
 #[derive(Debug)]
 pub struct Rope {
-	head: (i32, i32),
-	tail: (i32, i32),
+	knots: Vec<(i32, i32)>,
 	tails_visited_positions: HashSet<(i32, i32)>,
 }
 
-pub fn get_vectors_delta(v1: (i32, i32), v2: (i32, i32)) -> (i32, i32) {
+pub fn get_vectors_delta(v1: &(i32, i32), v2: &(i32, i32)) -> (i32, i32) {
 	(
 		max(v1.0, v2.0) - min(v1.0, v2.0),
 		max(v1.1, v2.1) - min(v1.1, v2.1),
 	)
 }
 
 impl Rope {
-	pub fn new() -> Self {
+	pub fn new(knots_count: u8, start_point: (i32, i32)) -> Self {
 		let mut tails_visited_positions = HashSet::new();
-		tails_visited_positions.insert((0, 0));
+		tails_visited_positions.insert(start_point);
+
+		let mut knots: Vec<(i32, i32)> = Vec::new();
+
+		for _ in 0..knots_count {
+			knots.push(start_point);
+		}
 
 		Self {
-			head: (0, 0),
-			tail: (0, 0),
+			knots,
 			tails_visited_positions,
 		}
 	}
 
-	fn get_rope_state(&self) -> (bool, (i32, i32)) {
-		let delta = get_vectors_delta(self.head, self.tail);
-		return (!(delta.0 > 1 || delta.1 > 1), delta);
+	fn is_ropes_touch(delta: &(i32, i32)) -> bool {
+		return !(delta.0 > 1 || delta.1 > 1);
 	}
 
-	pub fn move_tail_to_head(&mut self, delta: (i32, i32)) {
+	pub fn move_knot(&mut self, delta: &(i32, i32), top_knot_index: usize) {
 		if delta.0 >= 1 {
-			if self.head.0 > self.tail.0 {
-				self.tail.0 += 1;
+			if self.knots[top_knot_index].0 > self.knots[top_knot_index + 1].0 {
+				self.knots[top_knot_index + 1].0 += 1;
 			} else {
-				self.tail.0 -= 1;
+				self.knots[top_knot_index + 1].0 -= 1;
 			}
 		}
 
 		if delta.1 >= 1 {
-			if self.head.1 > self.tail.1 {
-				self.tail.1 += 1;
+			if self.knots[top_knot_index].1 > self.knots[top_knot_index + 1].1 {
+				self.knots[top_knot_index + 1].1 += 1;
 			} else {
-				self.tail.1 -= 1;
+				self.knots[top_knot_index + 1].1 -= 1;
 			}
 		}
 	}
 
 	pub fn apply_motion(&mut self, motion: &Motion) {
 		match *motion {
-			Motion::Down => self.head.1 -= 1,
-			Motion::Left => self.head.0 -= 1,
-			Motion::Right => self.head.0 += 1,
-			Motion::Up => self.head.1 += 1,
+			Motion::Down => self.knots[0].1 -= 1,
+			Motion::Left => self.knots[0].0 -= 1,
+			Motion::Right => self.knots[0].0 += 1,
+			Motion::Up => self.knots[0].1 += 1,
 		}
 
-		let (is_touch, delta) = self.get_rope_state();
+		let mut iter = (0..self.knots.len() - 1).into_iter();
+
+		loop {
+			let i = match iter.next() {
+				Some(i) => i,
+				None => break,
+			};
 
-		if !is_touch {
-			self.move_tail_to_head(delta);
-			self.tails_visited_positions.insert(self.tail);
+			let delta = get_vectors_delta(&self.knots[i], &self.knots[i + 1]);
+
+			if Rope::is_ropes_touch(&delta) {
+				break;
+			}
+
+			self.move_knot(&delta, i);
 		}
+
+		self
+			.tails_visited_positions
+			.insert(*self.knots.last().unwrap());
 	}
 
 	pub fn get_tails_visited_positions(&self) -> usize {
 		self.tails_visited_positions.len()
 	}
+
+	pub fn print_rope(&self) {
+		let y_range = -16..16;
+		let x_range = -16..16;
+
+		for y in y_range.rev() {
+			for x in x_range.clone() {
+				let i = self.knots.iter().position(|&p| p == (x + 1, y + 1));
+				match i {
+					Some(i) => print!("{i}"),
+					None => print!("."),
+				}
+			}
+			print!("\n");
+		}
+	}
 }
 
 #[cfg(test)]
@@ -117,20 +151,24 @@ mod tests {
 	#[test]
 	fn demo() {
 		let input = "\
-			R 4\n\
-			U 4\n\
-			L 3\n\
-			D 1\n\
-			R 4\n\
-			D 1\n\
-			L 5\n\
-			R 2";
-
-		let mut rope = Rope::new();
+			R 5\n\
+			U 8\n\
+			L 8\n\
+			D 3\n\
+			R 17\n\
+			D 10\n\
+			L 25\n\
+			";
+
+		let mut rope = Rope::new(10, (0, 0));
 		let motions = parse_series_of_motions(input);
 
 		motions.iter().for_each(|motion| rope.apply_motion(motion));
 
-		assert_eq!(rope.tails_visited_positions.len(), 13);
+		rope.print_rope();
+
+		println!("{:?}", rope.knots);
+
+		assert_eq!(rope.tails_visited_positions.len(), 36);
 	}
 }