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2019: day03: refacto part 1

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This commit is contained in:
Antoine Martin 2019-12-03 10:22:56 +01:00
parent 0662208914
commit a4f54fec18
1 changed files with 28 additions and 47 deletions
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75
aoc2019/src/day03.rs
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@ -9,6 +9,7 @@ const INPUT: &str = include_str!("../input/day03.txt");
pub fn run() -> Result<()> {
println!("part 1: {}", part1(INPUT)?);
Ok(())
}
@ -44,10 +45,6 @@ impl FromStr for Move {
}
}
fn parse_path(line: &str) -> Result<Vec<Move>> {
line.trim_end().split(',').map(|m| m.parse()).collect()
}
fn path(mut a: (i64, i64), b: (i64, i64)) -> Vec<(i64, i64)> {
let mut res = Vec::new();
@ -70,6 +67,32 @@ fn path(mut a: (i64, i64), b: (i64, i64)) -> Vec<(i64, i64)> {
res
}
fn parse_path(line: &str) -> Result<HashSet<(i64, i64)>> {
let moves = line
.trim_end()
.split(',')
.map(|m| m.parse())
.collect::<Result<Vec<Move>>>()?;
let mut pos = (0, 0);
Ok(moves
.iter()
.flat_map(|mv| {
let new_pos = match mv {
Move::Up(dy) => (pos.0, pos.1 - dy),
Move::Down(dy) => (pos.0, pos.1 + dy),
Move::Left(dx) => (pos.0 - dx, pos.1),
Move::Right(dx) => (pos.0 + dx, pos.1),
};
let p = path(pos, new_pos);
pos = new_pos;
p
})
.collect())
}
fn manhattan_distance(a: (i64, i64), b: (i64, i64)) -> i64 {
(a.0 - b.0).abs() + (a.1 - b.1).abs()
}
@ -79,51 +102,9 @@ fn part1(input: &str) -> Result<i64> {
let first_path = parse_path(lines.next().ok_or_else(|| err!("missing line in input"))?)?;
let second_path = parse_path(lines.next().ok_or_else(|| err!("missing line in input"))?)?;
let mut first_x = 0;
let mut first_y = 0;
let mut second_x = 0;
let mut second_y = 0;
let mut first_locations = HashSet::new();
let mut cross_locations = HashSet::new();
for mv in first_path {
let new_pos = match mv {
Move::Up(dy) => (first_x, first_y - dy),
Move::Down(dy) => (first_x, first_y + dy),
Move::Left(dx) => (first_x - dx, first_y),
Move::Right(dx) => (first_x + dx, first_y),
};
for cell in path((first_x, first_y), new_pos) {
first_locations.insert(cell);
}
first_x = new_pos.0;
first_y = new_pos.1;
}
for mv in second_path {
let new_pos = match mv {
Move::Up(dy) => (second_x, second_y - dy),
Move::Down(dy) => (second_x, second_y + dy),
Move::Left(dx) => (second_x - dx, second_y),
Move::Right(dx) => (second_x + dx, second_y),
};
for cell in path((second_x, second_y), new_pos) {
if first_locations.contains(&cell) {
cross_locations.insert(cell);
}
}
second_x = new_pos.0;
second_y = new_pos.1;
}
let cross_locations = first_path.intersection(&second_path);
cross_locations
.iter()
.map(|(x, y)| manhattan_distance((*x, *y), (0, 0)))
.min()
.ok_or_else(|| err!("the cables never crossed !"))