// codesnip-guard: main fn main() { #![allow(unused_imports, unused_macros)] prepare_io!(_in_buf, scanner, _out); macro_rules ! print { ($ ($ arg : tt) *) => (:: std :: write ! (_out , $ ($ arg) *) . expect ("io error")) } macro_rules ! println { ($ ($ arg : tt) *) => (:: std :: writeln ! (_out , $ ($ arg) *) . expect ("io error")) } scan!(scanner, n, mut s: Chars, (g, c): {TreeGraphScanner::::new(n)}); let k = s.len(); let mut ans = 0usize; for _ in 0..2 { let mut lcs = vec![vec![0usize; k + 1]; n]; capture!( [lcs: &mut Vec>, s: &[char], c: &[char], k,], fn dfs(g: &UndirectedSparseGraph, u: usize, p: usize) { for a in g.adjacencies(u) { if a.to != p { let c = c[a.id]; let (dp, ndp) = lcs.get_distinct_mut((u, a.to)); for i in 0..k { chmax!(ndp[i + 1], dp[i] + (c == s[i]) as usize); chmax!(ndp[i + 1], ndp[i]); } dfs!()(g, a.to, u); } } } ); dfs(&g, 0, !0); s.reverse(); chmax!(ans, lcs.iter().map(|l| l[k]).max().unwrap_or_default()); } println!("{}", ans); } #[macro_export] macro_rules! prepare_io { ($ in_buf : ident , $ scanner : ident , $ out : ident) => { use std::io::{stdout, BufWriter, Write as _}; let $in_buf = read_stdin_all_unchecked(); let mut $scanner = Scanner::new(&$in_buf); let $out = stdout(); let mut $out = BufWriter::new($out.lock()); }; } // codesnip-guard: _echo pub fn echo( mut writer: impl std::io::Write, iter: impl IntoIterator, sep: impl std::fmt::Display, ) -> std::io::Result<()> { let mut iter = iter.into_iter(); if let Some(item) = iter.next() { write!(writer, "{}", item)?; } for item in iter { write!(writer, "{}{}", sep, item)?; } writeln!(writer) } // codesnip-guard: scanner pub fn read_stdin_all_unchecked() -> String { use std::io::Read as _; let mut buf = Vec::new(); std::io::stdin().read_to_end(&mut buf).expect("io error"); unsafe { String::from_utf8_unchecked(buf) } } pub fn read_stdin_line() -> String { let mut s = String::new(); std::io::stdin().read_line(&mut s).expect("io error"); s } pub trait IterScan: Sized { type Output; fn scan<'a, I: Iterator>(iter: &mut I) -> Option; } pub trait MarkedIterScan: Sized { type Output; fn mscan<'a, I: Iterator>(self, iter: &mut I) -> Option; } #[derive(Clone, Debug)] pub struct Scanner<'a> { iter: std::str::SplitAsciiWhitespace<'a>, } mod scanner_impls { use super::*; impl<'a> Scanner<'a> { #[inline] pub fn new(s: &'a str) -> Self { let iter = s.split_ascii_whitespace(); Self { iter } } #[inline] pub fn scan(&mut self) -> ::Output { ::scan(&mut self.iter).expect("scan error") } #[inline] pub fn mscan(&mut self, marker: T) -> ::Output { marker.mscan(&mut self.iter).expect("scan error") } #[inline] pub fn scan_vec(&mut self, size: usize) -> Vec<::Output> { (0..size) .map(|_| ::scan(&mut self.iter).expect("scan error")) .collect() } #[inline] pub fn iter<'b, T: IterScan>(&'b mut self) -> ScannerIter<'a, 'b, T> { ScannerIter { inner: self, _marker: std::marker::PhantomData, } } } macro_rules ! iter_scan_impls { ($ ($ t : ty) *) => { $ (impl IterScan for $ t { type Output = Self ; # [inline] fn scan <'a , I : Iterator < Item = &'a str >> (iter : & mut I) -> Option < Self > { iter . next () ?. parse ::<$ t > () . ok () } }) * } ; } iter_scan_impls ! (char u8 u16 u32 u64 usize i8 i16 i32 i64 isize f32 f64 u128 i128 String); macro_rules ! iter_scan_tuple_impl { ($ ($ T : ident) *) => { impl <$ ($ T : IterScan) ,*> IterScan for ($ ($ T ,) *) { type Output = ($ (<$ T as IterScan >:: Output ,) *) ; # [inline] fn scan <'a , It : Iterator < Item = &'a str >> (_iter : & mut It) -> Option < Self :: Output > { Some (($ (<$ T as IterScan >:: scan (_iter) ?,) *)) } } } ; } iter_scan_tuple_impl!(); iter_scan_tuple_impl!(A); iter_scan_tuple_impl ! (A B); iter_scan_tuple_impl ! (A B C); iter_scan_tuple_impl ! (A B C D); iter_scan_tuple_impl ! (A B C D E); iter_scan_tuple_impl ! (A B C D E F); iter_scan_tuple_impl ! (A B C D E F G); iter_scan_tuple_impl ! (A B C D E F G H); iter_scan_tuple_impl ! (A B C D E F G H I); iter_scan_tuple_impl ! (A B C D E F G H I J); iter_scan_tuple_impl ! (A B C D E F G H I J K); pub struct ScannerIter<'a, 'b, T> { inner: &'b mut Scanner<'a>, _marker: std::marker::PhantomData T>, } impl<'a, 'b, T: IterScan> Iterator for ScannerIter<'a, 'b, T> { type Item = ::Output; #[inline] fn next(&mut self) -> Option { ::scan(&mut self.inner.iter) } } } #[derive(Debug, Copy, Clone)] pub struct Usize1; #[derive(Debug, Copy, Clone)] pub struct CharWithBase(pub char); #[derive(Debug, Copy, Clone)] pub struct Chars; #[derive(Debug, Copy, Clone)] pub struct CharsWithBase(pub char); #[derive(Debug, Copy, Clone)] pub struct Collect::Output>> { size: usize, _marker: std::marker::PhantomData (T, B)>, } mod marker_impls { use super::*; use std::{iter::FromIterator, marker::PhantomData}; impl IterScan for Usize1 { type Output = usize; #[inline] fn scan<'a, I: Iterator>(iter: &mut I) -> Option { ::scan(iter)?.checked_sub(1) } } impl MarkedIterScan for CharWithBase { type Output = usize; #[inline] fn mscan<'a, I: Iterator>(self, iter: &mut I) -> Option { Some((::scan(iter)? as u8 - self.0 as u8) as usize) } } impl IterScan for Chars { type Output = Vec; #[inline] fn scan<'a, I: Iterator>(iter: &mut I) -> Option { Some(iter.next()?.chars().collect()) } } impl MarkedIterScan for CharsWithBase { type Output = Vec; #[inline] fn mscan<'a, I: Iterator>(self, iter: &mut I) -> Option { Some( iter.next()? .chars() .map(|c| (c as u8 - self.0 as u8) as usize) .collect(), ) } } impl::Output>> Collect { pub fn new(size: usize) -> Self { Self { size, _marker: PhantomData, } } } impl::Output>> MarkedIterScan for Collect { type Output = B; #[inline] fn mscan<'a, I: Iterator>(self, iter: &mut I) -> Option { Some( (0..self.size) .map(|_| ::scan(iter).expect("scan error")) .collect::(), ) } } } #[macro_export] macro_rules ! scan_value { ($ scanner : expr , ($ ($ t : tt) ,*)) => { ($ ($ crate :: scan_value ! ($ scanner , $ t)) ,*) } ; ($ scanner : expr , [$ t : tt ; $ len : expr]) => { (0 ..$ len) . map (| _ | $ crate :: scan_value ! ($ scanner , $ t)) . collect ::< Vec < _ >> () } ; ($ scanner : expr , [$ t : ty ; $ len : expr]) => { $ scanner . scan_vec ::<$ t > ($ len) } ; ($ scanner : expr , [$ t : ty]) => { $ scanner . iter ::<$ t > () } ; ($ scanner : expr , { $ e : expr }) => { $ scanner . mscan ($ e) } ; ($ scanner : expr , $ t : ty) => { $ scanner . scan ::<$ t > () } ; } #[macro_export] macro_rules ! scan { ($ scanner : expr) => { } ; ($ scanner : expr ,) => { } ; ($ scanner : expr , mut $ var : tt : $ t : tt) => { let mut $ var = $ crate :: scan_value ! ($ scanner , $ t) ; } ; ($ scanner : expr , $ var : tt : $ t : tt) => { let $ var = $ crate :: scan_value ! ($ scanner , $ t) ; } ; ($ scanner : expr , mut $ var : tt : $ t : tt , $ ($ rest : tt) *) => { let mut $ var = $ crate :: scan_value ! ($ scanner , $ t) ; scan ! ($ scanner , $ ($ rest) *) } ; ($ scanner : expr , $ var : tt : $ t : tt , $ ($ rest : tt) *) => { let $ var = $ crate :: scan_value ! ($ scanner , $ t) ; scan ! ($ scanner , $ ($ rest) *) } ; ($ scanner : expr , mut $ var : tt) => { let mut $ var = $ crate :: scan_value ! ($ scanner , usize) ; } ; ($ scanner : expr , $ var : tt) => { let $ var = $ crate :: scan_value ! ($ scanner , usize) ; } ; ($ scanner : expr , mut $ var : tt , $ ($ rest : tt) *) => { let mut $ var = $ crate :: scan_value ! ($ scanner , usize) ; scan ! ($ scanner , $ ($ rest) *) } ; ($ scanner : expr , $ var : tt , $ ($ rest : tt) *) => { let $ var = $ crate :: scan_value ! ($ scanner , usize) ; scan ! ($ scanner , $ ($ rest) *) } ; } // codesnip-guard: SparseGraph pub use sparse_graph::{ Adjacency, BidirectionalGraphScanner, BidirectionalSparseGraph, DirectedGraphScanner, DirectedSparseGraph, SparseGraph, TreeGraphScanner, UndirectedGraphScanner, UndirectedSparseGraph, }; pub mod sparse_graph { use super::*; use std::{iter, marker::PhantomData, ops, slice}; type Marker = PhantomData T>; #[derive(Clone, Copy, Debug, Default, Eq, PartialEq, Ord, PartialOrd, Hash)] pub struct DirectedEdge; #[derive(Clone, Copy, Debug, Default, Eq, PartialEq, Ord, PartialOrd, Hash)] pub struct UndirectedEdge; #[derive(Clone, Copy, Debug, Default, Eq, PartialEq, Ord, PartialOrd, Hash)] pub struct BidirectionalEdge; #[derive(Clone, Copy, Debug, Default, Eq, PartialEq, Ord, PartialOrd, Hash)] pub struct Adjacency { pub id: usize, pub to: usize, } impl Adjacency { pub fn new(id: usize, to: usize) -> Adjacency { Adjacency { id, to } } } /// Static Sparse Graph represented as Compressed Sparse Row. #[derive(Debug, Clone)] pub struct SparseGraph { vsize: usize, pub start: Vec, pub elist: Vec, pub edges: Vec<(usize, usize)>, _marker: Marker, } impl SparseGraph { /// Return the number of vertices. pub fn vertices_size(&self) -> usize { self.vsize } /// Return the number of edges. pub fn edges_size(&self) -> usize { self.edges.len() } /// Return an iterator over graph vertices. pub fn vertices(&self) -> ops::Range { 0..self.vertices_size() } /// Return a slice of adjacency vertices. pub fn adjacencies(&self, v: usize) -> slice::Iter<'_, Adjacency> { self.elist[self.start[v]..self.start[v + 1]].iter() } } pub trait SparseGraphConstruction: Sized { fn construct_graph(vsize: usize, edges: Vec<(usize, usize)>) -> SparseGraph; } impl SparseGraph { /// Construct graph from edges. pub fn from_edges(vsize: usize, edges: Vec<(usize, usize)>) -> Self { D::construct_graph(vsize, edges) } } impl SparseGraphConstruction for DirectedEdge { fn construct_graph(vsize: usize, edges: Vec<(usize, usize)>) -> SparseGraph { let mut start: Vec<_> = iter::repeat(0).take(vsize + 1).collect(); let mut elist = Vec::with_capacity(edges.len()); unsafe { elist.set_len(edges.len()) } for (from, _) in edges.iter().cloned() { start[from] += 1; } for i in 1..=vsize { start[i] += start[i - 1]; } for (id, (from, to)) in edges.iter().cloned().enumerate() { start[from] -= 1; elist[start[from]] = Adjacency::new(id, to); } SparseGraph { vsize, start, elist, edges, _marker: PhantomData, } } } impl SparseGraphConstruction for UndirectedEdge { fn construct_graph(vsize: usize, edges: Vec<(usize, usize)>) -> SparseGraph { let mut start: Vec<_> = iter::repeat(0).take(vsize + 1).collect(); let mut elist = Vec::with_capacity(edges.len() * 2); unsafe { elist.set_len(edges.len() * 2) } for (from, to) in edges.iter().cloned() { start[to] += 1; start[from] += 1; } for i in 1..=vsize { start[i] += start[i - 1]; } for (id, (from, to)) in edges.iter().cloned().enumerate() { start[from] -= 1; elist[start[from]] = Adjacency::new(id, to); start[to] -= 1; elist[start[to]] = Adjacency::new(id, from); } SparseGraph { vsize, start, elist, edges, _marker: PhantomData, } } } impl SparseGraphConstruction for BidirectionalEdge { fn construct_graph(vsize: usize, edges: Vec<(usize, usize)>) -> SparseGraph { let mut start: Vec<_> = iter::repeat(0).take(vsize + 1).collect(); let mut elist = Vec::with_capacity(edges.len() * 2); unsafe { elist.set_len(edges.len() * 2) } for (from, to) in edges.iter().cloned() { start[to] += 1; start[from] += 1; } for i in 1..=vsize { start[i] += start[i - 1]; } for (id, (from, to)) in edges.iter().cloned().enumerate() { start[from] -= 1; elist[start[from]] = Adjacency::new(id * 2, to); start[to] -= 1; elist[start[to]] = Adjacency::new(id * 2 + 1, from); } SparseGraph { vsize, start, elist, edges, _marker: PhantomData, } } } pub type DirectedSparseGraph = SparseGraph; pub type UndirectedSparseGraph = SparseGraph; pub type BidirectionalSparseGraph = SparseGraph; pub struct SparseGraphScanner, T: IterScan, D> { vsize: usize, esize: usize, _marker: Marker<(U, T, D)>, } impl, T: IterScan, D> SparseGraphScanner { pub fn new(vsize: usize, esize: usize) -> Self { Self { vsize, esize, _marker: PhantomData, } } } impl, T: IterScan, D: SparseGraphConstruction> MarkedIterScan for SparseGraphScanner { type Output = (SparseGraph, Vec<::Output>); fn mscan<'a, I: Iterator>(self, iter: &mut I) -> Option { let mut edges = Vec::with_capacity(self.esize); let mut rest = Vec::with_capacity(self.esize); for _ in 0..self.esize { edges.push((U::scan(iter)?, U::scan(iter)?)); rest.push(T::scan(iter)?); } let graph = SparseGraph::from_edges(self.vsize, edges); Some((graph, rest)) } } pub type DirectedGraphScanner = SparseGraphScanner; pub type UndirectedGraphScanner = SparseGraphScanner; pub type BidirectionalGraphScanner = SparseGraphScanner; pub struct TreeGraphScanner, T: IterScan> { vsize: usize, _marker: Marker<(U, T)>, } impl, T: IterScan> TreeGraphScanner { pub fn new(vsize: usize) -> Self { Self { vsize, _marker: PhantomData, } } } impl, T: IterScan> MarkedIterScan for TreeGraphScanner { type Output = (UndirectedSparseGraph, Vec<::Output>); fn mscan<'a, I: Iterator>(self, iter: &mut I) -> Option { UndirectedGraphScanner::::new(self.vsize, self.vsize - 1).mscan(iter) } } } // codesnip-guard: capture #[macro_export] macro_rules ! capture { ([$ ($ ca : tt) *] , fn $ name : ident ($ ($ arg : tt) *) -> $ ret : ty $ body : block) => { capture ! ({ } [$ ($ ca) *,] fn $ name ($ ($ arg) *) -> $ ret $ body) } ; ([$ ($ ca : tt) *] , fn $ name : ident ($ ($ arg : tt) *) $ body : block) => { capture ! ({ } [$ ($ ca) *,] fn $ name ($ ($ arg) *) -> () $ body) } ; ({ $ (($ g : ident , $ ga : expr , $ gt : ty)) * } [] fn $ name : ident ($ ($ a : ident : $ at : ty) ,*) -> $ ret : ty $ body : block) => { fn $ name ($ ($ g : $ gt ,) * $ ($ a : $ at ,) *) -> $ ret { # [allow (unused_macros)] macro_rules ! $ name { () => { |$ ($ a) ,*| $ name ($ ($ g ,) * $ ($ a ,) *) } } $ body } # [allow (unused_mut)] let mut $ name = |$ ($ a) ,*| $ name ($ ($ ga ,) * $ ($ a ,) *) ; } ; ({ $ ($ g : tt) * } [] fn $ name : ident ($ ($ a : ident : $ at : ty) ,*,) $ ($ rest : tt) *) => { capture ! ({ $ ($ g) * } [] fn $ name ($ ($ a : $ at) ,*) $ ($ rest) *) } ; ({ $ ($ done : tt) * } [,] $ ($ rest : tt) *) => { capture ! ({ $ ($ done) * } [] $ ($ rest) *) } ; ({ $ ($ done : tt) * } [$ g : ident : & mut $ gt : ty , $ ($ rest : tt) *] $ ($ info : tt) *) => { capture ! ({ $ ($ done) * ($ g , & mut $ g , & mut $ gt) } [$ ($ rest) *] $ ($ info) *) } ; ({ $ ($ done : tt) * } [$ g : ident : &$ gt : ty , $ ($ rest : tt) *] $ ($ info : tt) *) => { capture ! ({ $ ($ done) * ($ g , &$ g , &$ gt) } [$ ($ rest) *] $ ($ info) *) } ; ({ $ ($ done : tt) * } [$ g : ident : $ gt : ty , $ ($ rest : tt) *] $ ($ info : tt) *) => { capture ! ({ $ ($ done) * ($ g , $ g , $ gt) } [$ ($ rest) *] $ ($ info) *) } ; ({ $ ($ done : tt) * } [$ g : ident , $ ($ rest : tt) *] $ ($ info : tt) *) => { capture ! ({ $ ($ done) * ($ g , $ g , usize) } [$ ($ rest) *] $ ($ info) *) } ; } // codesnip-guard: GetDistinctMut pub trait GetDistinctMut { type Output; fn get_distinct_mut(self, index: I) -> Self::Output; } impl<'a, T> GetDistinctMut<(usize, usize)> for &'a mut [T] { type Output = (&'a mut T, &'a mut T); fn get_distinct_mut(self, (i0, i1): (usize, usize)) -> Self::Output { assert_ne!(i0, i1); assert!(i0 < self.len()); assert!(i1 < self.len()); let ptr = self.as_mut_ptr(); unsafe { (&mut *ptr.add(i0), &mut *ptr.add(i1)) } } } impl<'a, T> GetDistinctMut<(usize, usize, usize)> for &'a mut [T] { type Output = (&'a mut T, &'a mut T, &'a mut T); fn get_distinct_mut(self, (i0, i1, i2): (usize, usize, usize)) -> Self::Output { assert_ne!(i0, i1); assert_ne!(i0, i2); assert!(i0 < self.len()); assert!(i1 < self.len()); assert!(i2 < self.len()); let ptr = self.as_mut_ptr(); unsafe { (&mut *ptr.add(i0), &mut *ptr.add(i1), &mut *ptr.add(i2)) } } } // codesnip-guard: ord_tools pub trait PartialOrdExt: Sized { fn chmin(&mut self, other: Self); fn chmax(&mut self, other: Self); fn minmax(self, other: Self) -> (Self, Self); } impl PartialOrdExt for T where T: PartialOrd, { #[inline] fn chmin(&mut self, other: Self) { if *self > other { *self = other; } } #[inline] fn chmax(&mut self, other: Self) { if *self < other { *self = other; } } #[inline] fn minmax(self, other: Self) -> (Self, Self) { if self < other { (self, other) } else { (other, self) } } } #[macro_export] macro_rules ! min { ($ l : expr) => { $ l } ; ($ l : expr ,) => { $ crate :: min ! ($ l) } ; ($ l : expr , $ r : expr) => { ($ l) . min ($ r) } ; ($ l : expr , $ r : expr ,) => { $ crate :: min ! ($ l , $ r) } ; ($ l : expr , $ r : expr , $ ($ t : tt) *) => { $ crate :: min ! ($ crate :: min ! ($ l , $ r) , $ ($ t) *) } ; } #[macro_export] macro_rules ! chmin { ($ l : expr) => { } ; ($ l : expr ,) => { } ; ($ l : expr , $ r : expr) => { { let r = $ r ; if $ l > r { $ l = r ; } } } ; ($ l : expr , $ r : expr ,) => { $ crate :: chmin ! ($ l , $ r) } ; ($ l : expr , $ r : expr , $ ($ t : tt) *) => { $ crate :: chmin ! ($ l , $ r) ; $ crate :: chmin ! ($ l , $ ($ t) *) } ; } #[macro_export] macro_rules ! max { ($ l : expr) => { $ l } ; ($ l : expr ,) => { $ crate :: max ! ($ l) } ; ($ l : expr , $ r : expr) => { ($ l) . max ($ r) } ; ($ l : expr , $ r : expr ,) => { $ crate :: max ! ($ l , $ r) } ; ($ l : expr , $ r : expr , $ ($ t : tt) *) => { $ crate :: max ! ($ crate :: max ! ($ l , $ r) , $ ($ t) *) } ; } #[macro_export] macro_rules ! chmax { ($ l : expr) => { } ; ($ l : expr ,) => { } ; ($ l : expr , $ r : expr) => { { let r = $ r ; if $ l < r { $ l = r ; } } } ; ($ l : expr , $ r : expr ,) => { $ crate :: chmax ! ($ l , $ r) } ; ($ l : expr , $ r : expr , $ ($ t : tt) *) => { $ crate :: chmax ! ($ l , $ r) ; $ crate :: chmax ! ($ l , $ ($ t) *) } ; } #[macro_export] macro_rules ! minmax { ($ ($ t : tt) *) => { ($ crate :: min ! ($ ($ t) *) , $ crate :: max ! ($ ($ t) *)) } ; }