87 lines
2.1 KiB
Rust
87 lines
2.1 KiB
Rust
//! Day 05 of 2020.
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use crate::prelude::*;
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/// Get the solution for day 05 of 2020.
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pub fn solution() -> Solution {
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Solution::new(Day::new(5, 2020), part_1, part_2).with_expected(850, 599)
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}
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/// The maximum range of rows.
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const MAX_ROW_RANGE: i32 = 128;
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/// The maximum range of columns.
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const MAX_COLUMN_RANGE: i32 = 8;
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/// Calculate the row and column from the input according to the puzzle's
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/// instructions.
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fn calculate_row_and_column(input: &str) -> (i32, i32) {
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let mut row_range = 0..MAX_ROW_RANGE;
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let mut column_range = 0..MAX_COLUMN_RANGE;
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for character in input.chars() {
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let row_min = row_range.start;
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let row_max = row_range.end;
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let row_difference = (row_max - row_min) / 2;
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let column_min = column_range.start;
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let column_max = column_range.end;
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let column_difference = (column_max - column_min) / 2;
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match character {
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'F' => {
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row_range = row_min..(row_max - row_difference);
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}
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'B' => {
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row_range = (row_min + row_difference)..row_max;
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}
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'L' => {
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column_range = column_min..(column_max - column_difference);
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}
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'R' => {
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column_range = (column_min + column_difference)..column_max;
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}
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_ => unreachable!("{character}"),
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}
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}
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(row_range.start, column_range.start)
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}
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/// Calculate the sead ID by multiplying the row by 8 and adding the column.
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fn calculate_seat_id((row, column): (i32, i32)) -> i32 {
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(row * 8) + column
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}
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/// The logic to solve part one.
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fn part_1(input: &str) -> Result<String> {
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Ok(
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input
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.lines()
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.map(calculate_row_and_column)
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.map(calculate_seat_id)
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.max()
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.unwrap()
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.to_string(),
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)
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}
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/// The logic to solve part two.
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fn part_2(input: &str) -> Result<String> {
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let seat_ids = input
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.lines()
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.map(calculate_row_and_column)
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.map(calculate_seat_id)
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.collect::<Vec<i32>>();
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let max_seat_id = seat_ids.iter().max().unwrap();
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let min_seat_id = seat_ids.iter().min().unwrap();
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Ok(
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(*min_seat_id..*max_seat_id)
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.find(|index| !seat_ids.contains(index))
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.map(|id| id.to_string())
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.unwrap(),
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)
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}
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