fn main() { input! { h: usize, w: usize, s: [bytes; h], } let g = Grid::new(h, w); let bfs = |src: (usize, usize)| -> Vec> { let mut dp = vec![vec![h * w; w]; h]; dp[src.0][src.1] = 0; let mut deq = std::collections::VecDeque::new(); deq.push_back(src); while let Some((x, y)) = deq.pop_front() { let d = dp[x][y] + 1; for (x, y) in g.four(x, y) { if s[x][y] != b'#' && dp[x][y] > d { dp[x][y] = d; deq.push_back((x, y)); } } } dp }; let mut a = bfs((0, 0)); let mut b = bfs((h - 1, w - 1)); let mut ans = h + w; ans = ans.min(a[h - 1][w - 1]); for _ in 0..2 { let h = a.len(); let w = a[0].len(); for i in 1..h { let a = &a[i - 1]; let b = &b[i]; let mut val = ans + 10; for j in 0..w { val = val.min(a[j] - j); ans = ans.min(val + b[j] + j + 2); } } a = transpose(a); b = transpose(b); } println!("{}", ans); } #[derive(Clone)] pub struct Grid { h: usize, w: usize, } impl Grid { pub fn new(h: usize, w: usize) -> Self { Self { h, w } } pub fn four(&self, x: usize, y: usize) -> impl Iterator + '_ { const DX: [usize; 4] = [0, 1, 0, !0]; const DY: [usize; 4] = [1, 0, !0, 0]; self.generator(x, y, DX.iter().zip(DY.iter()).map(|p| (*p.0, *p.1))) } pub fn eight(&self, x: usize, y: usize) -> impl Iterator + '_ { const DX: [usize; 8] = [0, 1, 1, 1, 0, !0, !0, !0]; const DY: [usize; 8] = [1, 1, 0, !0, !0, !0, 0, 1]; self.generator(x, y, DX.iter().zip(DY.iter()).map(|p| (*p.0, *p.1))) } pub fn generator<'a, I>( &'a self, x: usize, y: usize, it: I, ) -> impl Iterator + 'a where I: Iterator + 'a, { it.map(move |p| (x.wrapping_add(p.0), y.wrapping_add(p.1))) .filter(|p| p.0 < self.h && p.1 < self.w) } } // ---------- begin input macro ---------- // reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 #[macro_export] macro_rules! input { (source = $s:expr, $($r:tt)*) => { let mut iter = $s.split_whitespace(); input_inner!{iter, $($r)*} }; ($($r:tt)*) => { let s = { use std::io::Read; let mut s = String::new(); std::io::stdin().read_to_string(&mut s).unwrap(); s }; let mut iter = s.split_whitespace(); input_inner!{iter, $($r)*} }; } #[macro_export] macro_rules! input_inner { ($iter:expr) => {}; ($iter:expr, ) => {}; ($iter:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($iter, $t); input_inner!{$iter $($r)*} }; } #[macro_export] macro_rules! read_value { ($iter:expr, ( $($t:tt),* )) => { ( $(read_value!($iter, $t)),* ) }; ($iter:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($iter, $t)).collect::>() }; ($iter:expr, chars) => { read_value!($iter, String).chars().collect::>() }; ($iter:expr, bytes) => { read_value!($iter, String).bytes().collect::>() }; ($iter:expr, usize1) => { read_value!($iter, usize) - 1 }; ($iter:expr, $t:ty) => { $iter.next().unwrap().parse::<$t>().expect("Parse error") }; } // ---------- end input macro ---------- // ---------- begin transpose ---------- pub fn transpose(a: Vec>) -> Vec> { if a.is_empty() { return a; } let h = a.len(); let w = a[0].len(); assert!(a.iter().all(|a| a.len() == w)); let mut ta: Vec<_> = (0..w).map(|_| Vec::with_capacity(h)).collect(); for a in a { for (ta, a) in ta.iter_mut().zip(a) { ta.push(a); } } ta } // ---------- end transpose ----------