結果
問題 | No.1813 Magical Stones |
ユーザー |
|
提出日時 | 2023-04-01 10:27:35 |
言語 | Rust (1.83.0 + proconio) |
結果 |
AC
|
実行時間 | 142 ms / 2,000 ms |
コード長 | 5,253 bytes |
コンパイル時間 | 13,477 ms |
コンパイル使用メモリ | 400,584 KB |
実行使用メモリ | 23,928 KB |
最終ジャッジ日時 | 2024-09-24 09:13:40 |
合計ジャッジ時間 | 18,671 ms |
ジャッジサーバーID (参考情報) |
judge4 / judge1 |
(要ログイン)
ファイルパターン | 結果 |
---|---|
sample | AC * 4 |
other | AC * 40 |
ソースコード
use std::cmp::*;// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8macro_rules! input {($($r:tt)*) => {let stdin = std::io::stdin();let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));let mut next = move || -> String{bytes.by_ref().map(|r|r.unwrap() as char).skip_while(|c|c.is_whitespace()).take_while(|c|!c.is_whitespace()).collect()};input_inner!{next, $($r)*}};}macro_rules! input_inner {($next:expr) => {};($next:expr,) => {};($next:expr, $var:ident : $t:tt $($r:tt)*) => {let $var = read_value!($next, $t);input_inner!{$next $($r)*}};}macro_rules! read_value {($next:expr, ( $($t:tt),* )) => { ($(read_value!($next, $t)),*) };($next:expr, [ $t:tt ; $len:expr ]) => {(0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()};($next:expr, usize1) => (read_value!($next, usize) - 1);($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error"));}// Strong connected components.// This struct uses O(n) stack space.// Verified by: yukicoder No.470 (http://yukicoder.me/submissions/145785)// ABC214-H (https://atcoder.jp/contests/abc214/submissions/25082618)pub struct SCC {n: usize,ncc: usize,g: Vec<Vec<usize>>, // graph in adjacent listrg: Vec<Vec<usize>>, // reverse graphcmp: Vec<usize>, // topological order}impl SCC {pub fn new(n: usize) -> Self {SCC {n: n,ncc: n + 1,g: vec![Vec::new(); n],rg: vec![Vec::new(); n],cmp: vec![0; n],}}pub fn add_edge(&mut self, from: usize, to: usize) {self.g[from].push(to);self.rg[to].push(from);}fn dfs(&self, v: usize, used: &mut [bool], vs: &mut Vec<usize>) {used[v] = true;for &w in self.g[v].iter() {if !used[w] {self.dfs(w, used, vs);}}vs.push(v);}fn rdfs(&self, v: usize, k: usize,used: &mut [bool], cmp: &mut [usize]) {used[v] = true;cmp[v] = k;for &w in self.rg[v].iter() {if !used[w] {self.rdfs(w, k, used, cmp);}}}pub fn scc(&mut self) -> usize {let n = self.n;let mut used = vec![false; n];let mut vs = Vec::new();let mut cmp = vec![0; n];for v in 0..n {if !used[v] { self.dfs(v, &mut used, &mut vs); }}for u in used.iter_mut() {*u = false;}let mut k = 0;for &t in vs.iter().rev() {if !used[t] { self.rdfs(t, k, &mut used, &mut cmp); k += 1; }}self.ncc = k;self.cmp = cmp;k}pub fn top_order(&self) -> Vec<usize> {assert!(self.ncc <= self.n);self.cmp.clone()}// Returns a dag whose vertices are scc's, and whose edges are those of the original graph.pub fn dag(&self) -> Vec<Vec<usize>> {assert!(self.ncc <= self.n);let ncc = self.ncc;let mut ret = vec![vec![]; ncc];let n = self.n;for i in 0..n {for &to in self.g[i].iter() {if self.cmp[i] != self.cmp[to] {assert!(self.cmp[i] < self.cmp[to]);ret[self.cmp[i]].push(self.cmp[to]);}}}ret.into_iter().map(|mut v| {v.sort_unstable(); v.dedup();v}).collect()}pub fn rdag(&self) -> Vec<Vec<usize>> {assert!(self.ncc <= self.n);let ncc = self.ncc;let mut ret = vec![vec![]; ncc];let n = self.n;for i in 0..n {for &to in self.g[i].iter() {if self.cmp[i] != self.cmp[to] {assert!(self.cmp[i] < self.cmp[to]);ret[self.cmp[to]].push(self.cmp[i]);}}}ret.into_iter().map(|mut v| {v.sort_unstable(); v.dedup();v}).collect()}}fn main() {// In order to avoid potential stack overflow, spawn a new thread.let stack_size = 104_857_600; // 100 MBlet thd = std::thread::Builder::new().stack_size(stack_size);thd.spawn(|| solve()).unwrap().join().unwrap();}// https://yukicoder.me/problems/no/1813 (3.5)// SCC を行う。SCC が 1 個であれば 0。// SCC が 2 個以上の場合、SCC からなる DAG において max(入次数 0 の頂点数, 出次数 0 の頂点数) が答え。// これらの間に完全マッチングに近いものが作れるため。fn solve() {input! {n: usize, m: usize,ab: [(usize1, usize1); m],}let mut scc = SCC::new(n);for (a, b) in ab {scc.add_edge(a, b);}let ncc = scc.scc();let mut ans = 0;if ncc >= 2 {let dag = scc.dag();let rdag = scc.rdag();ans = max(dag.iter().filter(|x| x.is_empty()).count(), rdag.iter().filter(|x| x.is_empty()).count())}println!("{}", ans);}