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use anyhow::Context as _;
use std::convert::TryInto as _;
pub fn part1() -> anyhow::Result<i64> {
let input = crate::util::read_file_str("data/5.txt")?;
let mut max = 0;
for line in input.lines() {
let id = seat_id(line)?;
if id > max {
max = id;
}
}
Ok(max)
}
pub fn part2() -> anyhow::Result<i64> {
let mut seats = vec![false; 1024];
let input = crate::util::read_file_str("data/5.txt")?;
for line in input.lines() {
let id = seat_id(line)?;
seats[id as usize] = true;
}
let first = seats
.iter()
.position(|b| *b)
.context("failed to find taken seat")?;
let seat = seats
.iter()
.skip(first)
.position(|b| !*b)
.context("failed to find free seat")?
+ first;
if !seats[seat - 1] || seats[seat] || !seats[seat + 1] {
return Err(anyhow::anyhow!("invalid seat found"));
}
Ok(seat.try_into()?)
}
fn seat_id(desc: &str) -> anyhow::Result<i64> {
if desc.len() != 10 {
return Err(anyhow::anyhow!("invalid desc {}", desc));
}
let row_desc = &desc[0..7];
let col_desc = &desc[7..10];
let mut min_row = 0;
let mut max_row = 127;
for c in row_desc.chars() {
let mid = (max_row + min_row) / 2;
match c {
'F' => {
max_row = mid;
}
'B' => {
min_row = mid + 1;
}
_ => return Err(anyhow::anyhow!("invalid desc {}", desc)),
}
}
if min_row != max_row {
return Err(anyhow::anyhow!("bug"));
}
let row = min_row;
let mut min_col = 0;
let mut max_col = 7;
for c in col_desc.chars() {
let mid = (max_col + min_col) / 2;
match c {
'L' => {
max_col = mid;
}
'R' => {
min_col = mid + 1;
}
_ => return Err(anyhow::anyhow!("invalid desc {}", desc)),
}
}
if min_col != max_col {
return Err(anyhow::anyhow!("bug"));
}
let col = min_col;
Ok(row * 8 + col)
}
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