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make tuples immutable

This commit is contained in:
kageru 2022-12-09 13:05:41 +01:00
parent 98ebcaecb4
commit 3055794744
1 changed files with 9 additions and 16 deletions
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25
2022/src/bin/day09.rs
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@ -24,7 +24,7 @@ fn rope<const KNOTS: usize>(parsed: &Parsed) -> usize {
let mut positions = HashSet::default();
positions.insert((0, 0));
for &(dir, n) in parsed {
for _ in 0..n {
'outer: for _ in 0..n {
match dir {
b'U' => knots[0].1 += 1,
b'D' => knots[0].1 -= 1,
@ -32,33 +32,26 @@ fn rope<const KNOTS: usize>(parsed: &Parsed) -> usize {
b'R' => knots[0].0 += 1,
_ => unreachable!(),
}
let mut tail_moved = true;
for i in 0..KNOTS - 1 {
let ro = knots[i];
if !step_towards(&mut knots[i + 1], ro) {
tail_moved = false;
break;
if let Some(p) = step_towards(knots[i + 1], knots[i]) {
knots[i + 1] = p;
} else {
continue 'outer;
}
}
if tail_moved {
positions.insert(knots[KNOTS - 1]);
}
positions.insert(knots[KNOTS - 1]);
}
}
positions.len()
}
#[inline]
fn step_towards(tail: &mut (i32, i32), head: (i32, i32)) -> bool {
fn step_towards(tail: (i32, i32), head: (i32, i32)) -> Option<(i32, i32)> {
let xdiff = head.0 - tail.0;
let ydiff = head.1 - tail.1;
match (xdiff, ydiff) {
(-1 | 0 | 1, -1 | 0 | 1) => false,
_ => {
tail.0 += xdiff.signum();
tail.1 += ydiff.signum();
true
}
(-1 | 0 | 1, -1 | 0 | 1) => None,
_ => Some((tail.0 + xdiff.signum(), tail.1 + ydiff.signum())),
}
}