126 lines
4 KiB
Rust
126 lines
4 KiB
Rust
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#![feature(let_chains)]
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use itertools::Itertools;
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#[derive(Debug, PartialEq)]
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enum Block {
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Start { position: u64 },
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End { position: u64 },
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Track { position: u64 },
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Wall,
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}
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const GRID_SIZE: usize = 141;
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// const GRID_SIZE: usize = 15;
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const INPUT: &str = include_str!("input.txt");
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fn main() {
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let (mut start, mut end) = ((0_usize, 0_usize), (0_usize, 0_usize));
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let mut grid: [[Block; GRID_SIZE]; GRID_SIZE] = INPUT
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.lines()
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.enumerate()
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.map(|(row, l)| {
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l.chars()
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.enumerate()
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.map(|(col, c)| match c {
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'S' => {
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start = (row, col);
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Block::Start { position: 0 }
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}
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'E' => {
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end = (row, col);
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Block::End { position: u64::MAX }
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}
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'.' => Block::Track { position: u64::MAX },
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'#' => Block::Wall,
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_ => unreachable!(),
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})
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.collect_vec()
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.try_into()
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.unwrap()
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})
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.collect_vec()
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.try_into()
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.unwrap();
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// Run the track, setting the index of the specific block each time
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let mut cur = start;
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let mut i = 0_u64;
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while grid[cur.0][cur.1] != (Block::End { position: u64::MAX }) {
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// Set current index
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if let Block::Track { ref mut position } = grid[cur.0][cur.1] {
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*position = i;
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}
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// Find the next one and move to it
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if let Block::Track { position } | Block::End { position } = grid[cur.0 + 1][cur.1]
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&& position == u64::MAX
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{
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cur = (cur.0 + 1, cur.1);
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} else if let Block::Track { position } | Block::End { position } = grid[cur.0 - 1][cur.1]
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&& position == u64::MAX
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{
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cur = (cur.0 - 1, cur.1);
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} else if let Block::Track { position } | Block::End { position } = grid[cur.0][cur.1 - 1]
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&& position == u64::MAX
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{
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cur = (cur.0, cur.1 - 1);
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} else if let Block::Track { position } | Block::End { position } = grid[cur.0][cur.1 + 1]
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&& position == u64::MAX
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{
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cur = (cur.0, cur.1 + 1);
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} else {
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unreachable!();
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}
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// Increment and continue
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i += 1;
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}
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// Set end position too
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if let Block::End { ref mut position } = grid[cur.0][cur.1] {
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*position = i;
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} else {
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unreachable!();
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}
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// Iterate over it again, this time checking if a cheat is skipping more than 100
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// Run the track, setting the index of the specific block each time
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let mut sum = 0;
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for row in 0..GRID_SIZE {
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for col in 0..GRID_SIZE {
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let (Block::Start {
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position: cur_position,
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}
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| Block::End {
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position: cur_position,
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}
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| Block::Track {
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position: cur_position,
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}) = grid[row][col]
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else {
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continue;
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};
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// Check all points that
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for end_row in 0..GRID_SIZE {
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for end_col in 0..GRID_SIZE {
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// 1. Are within 20 manhattan distance
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let manhattan: u64 =
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(if end_row > row { end_row - row } else { row - end_row }
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+ if end_col > col { end_col - col } else { col - end_col }).try_into().unwrap();
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if manhattan > 20 { continue; }
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// 2. Would save time by ignoring walls (end - start - manhattan-distance)
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if let Block::Track { position } | Block::End { position } = grid[end_row][end_col]
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&& position > cur_position
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&& (position - cur_position - manhattan) >= 100
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{
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sum += 1;
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}
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}
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}
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}
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}
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println!("Result: {sum}");
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}
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