AdventOfCode-2022/day9.chpl

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2022-12-08 22:19:40 -08:00
use IO, Set;
const moveList = [ "L" => (-1, 0), "R" => (1, 0), "U" => (0, 1), "D" => (0, -1) ];
iter moves() {
for line in stdin.lines().strip() {
const (dir, _, n) = line.partition(" ");
yield (moveList[dir], n : int);
}
}
config const length = 2;
var rope: [0..<length] (int, int) = (0, 0);
proc move((hx, hy), (tx, ty)): (int, int) {
const (dx, dy) = (hx - tx, hy - ty);
if abs(dx) > 1 && dy == 0 {
tx += sgn(dx);
} else if abs(dy) > 1 && dx == 0 {
ty += sgn(dy);
} else if abs(dx) + abs(dy) > 2 {
tx += sgn(dx);
ty += sgn(dy);
}
return (tx, ty);
}
var visited = new set((int, int));
for (delta, n) in moves() {
for 1..n {
rope[0] += delta;
for idx in 1..<length {
rope[idx] = move(rope[idx-1], rope[idx]);
}
visited.add(rope.last);
}
}
writeln(visited.size);