#[allow(unused_imports)] use std::cmp::*; #[allow(unused_imports)] use std::collections::*; use std::io::{Write, BufWriter}; // https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 macro_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, [graph1; $len:expr]) => {{ let mut g = vec![vec![]; $len]; let ab = read_value!($next, [(usize1, usize1)]); for (a, b) in ab { g[a].push(b); g[b].push(a); } g }}; ($next:expr, ( $($t:tt),* )) => { ( $(read_value!($next, $t)),* ) }; ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, chars) => { read_value!($next, String).chars().collect::>() }; ($next:expr, usize1) => (read_value!($next, usize) - 1); ($next:expr, [ $t:tt ]) => {{ let len = read_value!($next, usize); read_value!($next, [$t; len]) }}; ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error")); } #[allow(unused)] macro_rules! debug { ($($format:tt)*) => (write!(std::io::stderr(), $($format)*).unwrap()); } #[allow(unused)] macro_rules! debugln { ($($format:tt)*) => (writeln!(std::io::stderr(), $($format)*).unwrap()); } const INF: i64 = 1 << 50; /// Lowest Common Ancestor. Call lca(x, y) to get the lca of them. /// Many-rooted version. /// Verified by: https://yukicoder.me/submissions/413634 pub struct LowestCommonAncestor { n: usize, bn: usize, parent: Vec, // r is root <=> parent[r] = r dep: Vec, lca_tbl: Vec>, lca_tblm1: Vec>, acc: Vec, nobias: Vec>, bias: Vec>, sing: Vec<[(i64, usize); 3]>, } impl LowestCommonAncestor { fn dfs(&mut self, edges: &[Vec<(usize, i64)>], v: usize, par: usize, d: usize, accd: i64) { self.parent[v] = par; self.dep[v] = d; self.acc[v] = accd; let mut nobias_cand = vec![]; let mut sing_cand = vec![]; for &(u, c) in edges[v].iter() { if u != par { self.dfs(edges, u, v, d + 1, accd + c); nobias_cand.push((c, u)); sing_cand.push((c, u)); } else { sing_cand.push((c, v)); } } let r = min(3, sing_cand.len()); sing_cand.sort(); self.sing[v][..r].copy_from_slice(&sing_cand[..r]); let r = min(2, nobias_cand.len()); nobias_cand.sort(); self.nobias[v][0][..r].copy_from_slice(&nobias_cand[..r]); } fn lca_init(&mut self) { let n = self.n; for v in 0..n { if v == 0 { continue; } let pnobias = self.nobias[self.parent[v]][0]; let me = if pnobias[0].1 == v { pnobias[1] } else { pnobias[0] }; self.bias[v][0] = me; } for v in 0 .. n { self.lca_tbl[v] = vec![0; self.bn + 1]; self.lca_tbl[v][0] = self.parent[v]; self.lca_tblm1[v] = vec![0; self.bn + 1]; self.lca_tblm1[v][0] = v; } for i in 1 .. self.bn + 1 { for v in 0 .. n { let mid = self.lca_tbl[v][i - 1]; let midm1 = self.lca_tblm1[v][i - 1]; assert_eq!(self.parent[midm1], mid); self.lca_tbl[v][i] = self.lca_tbl[mid][i - 1]; self.lca_tblm1[v][i] = self.lca_tblm1[mid][i - 1]; self.bias[v][i] = min(self.bias[v][i - 1], self.bias[mid][i - 1]); let mut sub = self.nobias[v][i - 1].to_vec(); sub.push(self.bias[midm1][i - 1]); sub.sort(); self.nobias[v][i].copy_from_slice(&sub[..2]); } } } pub fn lca(&self, mut x: usize, mut y: usize) -> usize { let dx = self.dep[x]; let mut dy = self.dep[y]; if dx > dy { return self.lca(y, x); } for l in (0 .. self.bn + 1).rev() { if dy - dx >= 1 << l { y = self.lca_tbl[y][l]; dy -= 1 << l; } } assert_eq!(dx, dy); if x == y { return x; } for l in (0 .. self.bn + 1).rev() { if self.lca_tbl[x][l] != self.lca_tbl[y][l] { x = self.lca_tbl[x][l]; y = self.lca_tbl[y][l]; } } self.lca_tbl[x][0] } #[allow(unused)] pub fn depth(&self, a: usize) -> usize { self.dep[a] } #[allow(unused)] pub fn parent(&self, a: usize) -> usize { self.parent[a] } pub fn new(edges: &[Vec<(usize, i64)>], roots: &[usize]) -> Self { let n = edges.len(); let bn = (n.next_power_of_two() - 1).count_ones() as usize; let mut ret = LowestCommonAncestor { n: n, bn: bn, parent: vec![0; n], dep: vec![0; n], lca_tbl: vec![Vec::new(); n], lca_tblm1: vec![Vec::new(); n], acc: vec![0; n], nobias: vec![vec![[(INF, 0); 2]; bn + 1]; n], bias: vec![vec![(INF, 0); bn + 1]; n], sing: vec![[(INF, 0); 3]; n], }; for &r in roots { ret.dfs(edges, r, r, 0, 0); } ret.lca_init(); ret } } fn solve() { let out = std::io::stdout(); let mut out = BufWriter::new(out.lock()); macro_rules! puts { ($($format:tt)*) => (let _ = write!(out,$($format)*);); } input! { n: usize, uvw: [(usize1, usize1, i64); n - 1], q: usize, xy: [(usize1, usize1); q], } let mut g = vec![vec![]; n]; for &(u, v, w) in &uvw { g[u].push((v, w)); g[v].push((u, w)); } let lca = LowestCommonAncestor::new(&g, &[0]); for &(x, y) in &xy { assert_ne!(x, y); let l = lca.lca(x, y); let dist = lca.acc[x] + lca.acc[y] - 2 * lca.acc[l]; let ldep = lca.dep[l]; let xdep = lca.dep[x]; let ydep = lca.dep[y]; let mut mi = (INF, 0); let mut excl = [n; 2]; if ldep < xdep { let mut cur = x; mi = min(mi, lca.nobias[x][0][0]); for i in 0..lca.bn + 1 { if ((xdep - ldep - 1) & 1 << i) != 0 { mi = min(mi, lca.bias[cur][i]); cur = lca.lca_tbl[cur][i]; } } excl[0] = cur; } if ldep < ydep { let mut cur = y; mi = min(mi, lca.nobias[y][0][0]); for i in 0..lca.bn + 1 { if ((ydep - ldep - 1) & 1 << i) != 0 { mi = min(mi, lca.bias[cur][i]); cur = lca.lca_tbl[cur][i]; } } excl[1] = cur; } for j in 0..3 { let dat = lca.sing[l][j]; if excl[0] == dat.1 || excl[1] == dat.1 { continue; } mi = min(mi, dat); } puts!("{}\n", if mi.0 >= INF { -1 } else { dist + 2 * mi.0 }); } } fn main() { // In order to avoid potential stack overflow, spawn a new thread. let stack_size = 104_857_600; // 100 MB let thd = std::thread::Builder::new().stack_size(stack_size); thd.spawn(|| solve()).unwrap().join().unwrap(); }