コード
#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;
class LCA {
private:
LCA() {}
vector<vector<int>> G;
vector<vector<int>> parent;
vector<int> depth;
int root, logV;
public:
void dfs(int v, int p, int d) {
parent[0][v] = p;
depth[v] = d;
for (auto &u : G[v])
if (u != p) dfs(u, v, d + 1);
}
LCA(const vector<vector<int>> &adj) {
int V = adj.size();
root = 0;
G = adj;
depth.assign(V, 0);
logV = 1;
for (int i = 1; i <= V;) i *= 2, logV++;
parent.assign(logV, vector<int>(V));
dfs(root, -1, 0);
for (int k = 0; k + 1 < logV; ++k)
for (int v = 0; v < V; ++v)
if (parent[k][v] < 0) {
parent[k + 1][v] = -1;
} else {
parent[k + 1][v] = parent[k][parent[k][v]];
}
}
int getLCA(int u, int v) {
if (depth[u] > depth[v]) swap(u, v);
for (int k = 0; k < logV; ++k)
if ((depth[v] - depth[u]) >> k & 1) v = parent[k][v];
if (u == v) return u;
for (int k = logV - 1; k >= 0; --k)
if (parent[k][u] != parent[k][v]) {
u = parent[k][u];
v = parent[k][v];
}
return parent[0][u];
}
int getLength(int u, int v) {
int lca = getLCA(u, v);
return depth[u] + depth[v] - depth[lca] * 2;
}
};
int main() {
cin.tie(0);
ios::sync_with_stdio(false);
int N;
cin >> N;
vector<vector<int>> adj(N, vector<int>());
for (int i = 0; i < N - 1; ++i) {
int x, y;
cin >> x >> y;
x--, y--;
adj[x].push_back(y);
adj[y].push_back(x);
}
LCA lca(adj);
int Q;
cin >> Q;
for (int i = 0; i < Q; ++i) {
int x, y;
cin >> x >> y;
x--, y--;
cout << lca.getLength(x, y) + 1 << "\n";
}
}