#[doc = " https://github.com/hatoo/competitive-rust-snippets"] #[allow(unused_imports)] use std::cmp::{max, min, Ordering}; #[allow(unused_imports)] use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque}; #[allow(unused_imports)] use std::io::{stdin, stdout, BufWriter, Write}; #[allow(unused_imports)] use std::iter::FromIterator; #[allow(unused_macros)] macro_rules ! debug { ( $ ( $ a : expr ) ,* ) => { eprintln ! ( concat ! ( $ ( stringify ! ( $ a ) , " = {:?}, " ) ,* ) , $ ( $ a ) ,* ) ; } } #[macro_export] macro_rules ! input { ( source = $ s : expr , $ ( $ r : tt ) * ) => { let mut parser = Parser :: from_str ( $ s ) ; input_inner ! { parser , $ ( $ r ) * } } ; ( parser = $ parser : ident , $ ( $ r : tt ) * ) => { input_inner ! { $ parser , $ ( $ r ) * } } ; ( new_stdin_parser = $ parser : ident , $ ( $ r : tt ) * ) => { let stdin = std :: io :: stdin ( ) ; let reader = std :: io :: BufReader :: new ( stdin . lock ( ) ) ; let mut $ parser = Parser :: new ( reader ) ; input_inner ! { $ parser , $ ( $ r ) * } } ; ( $ ( $ r : tt ) * ) => { input ! { new_stdin_parser = parser , $ ( $ r ) * } } ; } #[macro_export] macro_rules ! input_inner { ( $ parser : ident ) => { } ; ( $ parser : ident , ) => { } ; ( $ parser : ident , $ var : ident : $ t : tt $ ( $ r : tt ) * ) => { let $ var = read_value ! ( $ parser , $ t ) ; input_inner ! { $ parser $ ( $ r ) * } } ; } #[macro_export] macro_rules ! read_value { ( $ parser : ident , ( $ ( $ t : tt ) ,* ) ) => { ( $ ( read_value ! ( $ parser , $ t ) ) ,* ) } ; ( $ parser : ident , [ $ t : tt ; $ len : expr ] ) => { ( 0 ..$ len ) . map ( | _ | read_value ! ( $ parser , $ t ) ) . collect ::< Vec < _ >> ( ) } ; ( $ parser : ident , chars ) => { read_value ! ( $ parser , String ) . chars ( ) . collect ::< Vec < char >> ( ) } ; ( $ parser : ident , usize1 ) => { read_value ! ( $ parser , usize ) - 1 } ; ( $ parser : ident , $ t : ty ) => { $ parser . next ::<$ t > ( ) . expect ( "Parse error" ) } ; } use std::io; use std::io::BufRead; use std::str; pub struct Parser { reader: R, buf: Vec, pos: usize, } impl Parser { pub fn from_str(s: &str) -> Parser { Parser { reader: io::empty(), buf: s.as_bytes().to_vec(), pos: 0, } } } impl Parser { pub fn new(reader: R) -> Parser { Parser { reader: reader, buf: vec![], pos: 0, } } pub fn update_buf(&mut self) { self.buf.clear(); self.pos = 0; loop { let (len, complete) = { let buf2 = self.reader.fill_buf().unwrap(); self.buf.extend_from_slice(buf2); let len = buf2.len(); if len == 0 { break; } (len, buf2[len - 1] <= 0x20) }; self.reader.consume(len); if complete { break; } } } pub fn next(&mut self) -> Result { loop { let mut begin = self.pos; while begin < self.buf.len() && (self.buf[begin] <= 0x20) { begin += 1; } let mut end = begin; while end < self.buf.len() && (self.buf[end] > 0x20) { end += 1; } if begin != self.buf.len() { self.pos = end; return str::from_utf8(&self.buf[begin..end]).unwrap().parse::(); } else { self.update_buf(); } } } } #[allow(unused_macros)] macro_rules ! debug { ( $ ( $ a : expr ) ,* ) => { eprintln ! ( concat ! ( $ ( stringify ! ( $ a ) , " = {:?}, " ) ,* ) , $ ( $ a ) ,* ) ; } } #[doc = " https://github.com/hatoo/competitive-rust-snippets"] const BIG_STACK_SIZE: bool = true; #[allow(dead_code)] fn main() { use std::thread; if BIG_STACK_SIZE { thread::Builder::new() .stack_size(32 * 1024 * 1024) .name("solve".into()) .spawn(solve) .unwrap() .join() .unwrap(); } else { solve(); } } fn ctoi(x: char) -> u64 { x as u64 - 'a' as u64 } fn solve() { input! { S: chars, } let s: Vec = S.iter().map(|&x| ctoi(x)).collect(); let rh = RollingHash::new(&s); let gamma = |i: usize, j: usize| { let h1 = rh.get(i, j); let h2 = rh.get(s.len()-j, s.len()-i); if h1 == h2 { 1 } else { 0 } }; let mid = s.len()/2; let mut dp = vec![0; mid+1]; dp[s.len()/2] = 1; for i in (0..mid).rev() { let mut sum = 1; // for i,i for j in (i+1..mid+1) { // dbg!(i,j,gamma(i,j)); sum += gamma(i,j) * dp[j]; } dp[i] = sum; } let dec = if s.len() % 2 == 0 { 1 } else { 0 }; println!("{}", dp[0]-dec); } #[allow(dead_code)] /// Rolling hash algorithm pub struct RollingHash { hash_pow_list: Vec<(u64, Vec<(u64, u64)>)>, } #[allow(dead_code)] impl RollingHash { pub fn new(s: &[u64]) -> RollingHash { RollingHash::with_base_mod_pairs(s, &[(1009, 1_000_000_007), (9973, 999_999_937)]) } pub fn with_base_mod_pairs(s: &[u64], base_mod_pairs: &[(u64, u64)]) -> RollingHash { let hp_list = base_mod_pairs .iter() .map(|&(base, m)| { let mut hp = Vec::with_capacity(s.len() + 1); hp.push((0, 1)); for (i, &x) in s.iter().enumerate() { let (h, p) = hp[i]; hp.push(((h + x) * base % m, p * base % m)); } (m, hp) }) .collect(); RollingHash { hash_pow_list: hp_list, } } // [l, r) pub fn get(&self, l: usize, r: usize) -> u64 { self.hash_pow_list .iter() .map(|&(m, ref hp)| (hp[r].0 + m - hp[l].0 * hp[r - l].1 % m) % m) .fold(0, |a, b| a ^ b) } pub fn len(&self) -> usize { self.hash_pow_list .first() .map(|v| v.1.len() - 1) .unwrap_or(0) } }