// 一つ選んで塗る操作をし切ってから過半数で塗る // // DPしようと思うと // 親が何であろうが黒にできる // 白のまま、親が黒である必要がある fn main() { input! { n: usize, e: [(usize1, usize1); n - 1], } for r in 0..1 { let mut hld = HLD::new(n); for &(a, b) in e.iter() { hld.add_edge(a, b); } hld.build(r); let mut dp = vec![(0i32, 0i32); n]; for i in (0..n).rev() { let v = hld.vertex(i); let mut c = hld.child[v].iter().map(|u| dp[*u]).collect::>(); c.sort_by_key(|p| p.0 - p.1); let neighbor = if v == r { c.len() } else { c.len() + 1 }; // 黒で塗る場合 let mut can = 1; for &(a, b) in c.iter() { can += a.min(b); } // 子から黒を伝播させられる時 if neighbor / 2 + 1 <= c.len() { let need = neighbor / 2 + 1; let (l, r) = c.split_at(need); let s = l.iter().map(|p| p.0).sum::() + r.iter().map(|p| p.1).sum::(); can = can.min(s); } dp[v].0 = can; // 親が黒であるなら可能な時 if v != r { let (l, r) = c.split_at(neighbor / 2); let s = l.iter().map(|p| p.0).sum::() + r.iter().map(|p| p.1).sum::(); dp[v].1 = s; } dp[v].1 = dp[v].1.min(dp[v].0); } println!("{}", dp[r].0); } } // ---------- 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 Heavy-Light decomposition ---------- pub struct HLD { size: usize, edge: Vec<(usize, usize)>, child: Vec>, path_root: Vec, parent: Vec, left: Vec, right: Vec, inverse: Vec, } impl HLD { pub fn new(size: usize) -> Self { assert!(size <= 10usize.pow(8)); HLD { size: size, edge: Vec::with_capacity(size - 1), child: Vec::new(), path_root: Vec::new(), parent: Vec::new(), left: Vec::new(), right: Vec::new(), inverse: Vec::new(), } } pub fn add_edge(&mut self, a: usize, b: usize) { assert!(a != b && a < self.size && b < self.size); self.edge.push((a, b)); } pub fn build(&mut self, root: usize) { assert!(self.edge.len() + 1 == self.size); let size = self.size; let mut cnt = vec![0; size]; for &(a, b) in self.edge.iter() { cnt[a] += 1; cnt[b] += 1; } let mut child = cnt .into_iter() .map(|c| Vec::with_capacity(c)) .collect::>(); for &(a, b) in self.edge.iter() { child[a].push(b); child[b].push(a); } let mut parent = vec![size; size]; let mut q = Vec::with_capacity(size); q.push(root); parent[root] = root; for i in 0..size { let v = q[i]; for u in child[v].clone() { assert!(parent[u] == size); parent[u] = v; child[u].retain(|e| *e != v); q.push(u); } } let mut sum = vec![1; size]; for &v in q.iter().rev() { let child = &mut child[v]; if !child.is_empty() { let (pos, _) = child.iter().enumerate().max_by_key(|p| sum[*p.1]).unwrap(); child.swap(0, pos); sum[v] = 1 + child.iter().fold(0, |s, a| s + sum[*a]); } } let mut path_root = (0..size).collect::>(); let mut left = vec![0; size]; let mut right = vec![0; size]; let mut dfs = vec![(root, false)]; let mut id = 0; while let Some((v, end)) = dfs.pop() { if end { right[v] = id; continue; } left[v] = id; id += 1; dfs.push((v, true)); let child = &child[v]; if !child.is_empty() { for &u in child[1..].iter() { path_root[u] = u; dfs.push((u, false)); } let u = child[0]; path_root[u] = path_root[v]; dfs.push((u, false)); } } let mut inverse = vec![size; size]; for (i, l) in left.iter().enumerate() { inverse[*l] = i; } self.child = child; self.parent = parent; self.left = left; self.right = right; self.path_root = path_root; self.inverse = inverse; } pub fn lca(&self, mut a: usize, mut b: usize) -> usize { assert!(a < self.size && b < self.size); let path = &self.path_root; let parent = &self.parent; let index = &self.left; while path[a] != path[b] { if index[a] > index[b] { std::mem::swap(&mut a, &mut b); } b = parent[path[b]]; } std::cmp::min((index[a], a), (index[b], b)).1 } pub fn path( &self, src: usize, dst: usize, up: &mut Vec<(usize, usize)>, down: &mut Vec<(usize, usize)>, ) { assert!(src < self.size && dst < self.size); up.clear(); down.clear(); let path = &self.path_root; let parent = &self.parent; let index = &self.left; let mut x = src; let mut y = dst; while path[x] != path[y] { if index[x] > index[y] { let p = path[x]; assert!(p == path[p]); up.push((index[p], index[x] + 1)); x = parent[p]; } else { let p = path[y]; assert!(p == path[p]); down.push((index[p], index[y] + 1)); y = parent[p]; } } if index[x] <= index[y] { down.push((index[x], index[y] + 1)); } else { up.push((index[y], index[x] + 1)); } down.reverse(); } pub fn sub_tree(&self, v: usize) -> (usize, usize) { assert!(v < self.size); (self.left[v], self.right[v]) } pub fn parent(&self, v: usize) -> Option { assert!(v < self.size); let p = self.parent[v]; if p == v { None } else { Some(p) } } // s -> t へのパスの2番目の頂点を返す pub fn next(&self, s: usize, t: usize) -> usize { assert!(s < self.size && t < self.size && s != t); let (a, b) = self.sub_tree(s); let (c, d) = self.sub_tree(t); if !(a <= c && d <= b) { return self.parent[s]; } let mut pos = t; let mut pre = t; while self.path_root[s] != self.path_root[pos] { pre = self.path_root[pos]; pos = self.parent[pre]; } if s == pos { pre } else { self.child[s][0] } } pub fn vertex(&self, x: usize) -> usize { assert!(x < self.size); self.inverse[x] } pub fn jump( &self, s: usize, t: usize, mut k: usize, up: &mut Vec<(usize, usize)>, down: &mut Vec<(usize, usize)>, ) -> Option { assert!(s.max(t) < self.size); self.path(s, t, up, down); for (l, r) in up.drain(..) { if k < r - l { return Some(self.vertex(r - 1 - k)); } k -= r - l; } for (l, r) in down.drain(..) { if k < r - l { return Some(self.vertex(l + k)); } k -= r - l; } None } } // ---------- end Heavy-Light decomposition ----------