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- #include<bits/stdc++.h>
- #include <ext/pb_ds/assoc_container.hpp>
- #include <ext/pb_ds/tree_policy.hpp>
- using namespace std;
- using namespace __gnu_pbds;
- #define debug(x) cerr << '[' << (#x) << "] = " << x << '\n';
- template<class T> using ordered_set = tree<T, null_type , less<T> , rb_tree_tag , tree_order_statistics_node_update> ;
- const int maxn = 50005;
- vector<pair<int,int>>g[maxn];
- void PlayGround() {
- int N; cin >> N;
- for(int i=1; i<N; ++i) {
- int u, v, w; cin >> u >> v >> w;
- g[u].push_back(make_pair(v, w));
- g[v].push_back(make_pair(u, w));
- }
- int l = 20, timer = 0;
- vector<int>dist(maxn), tin(maxn), tout(maxn);
- vector<vector<int>>up(N+5, vector<int>(l+1));
- function<void(int,int)> DFS = [&] (int node, int parent) {
- tin[node] = timer++;
- up[node][0] = parent;
- for(int i=1; i<=l; ++i)
- up[node][i] = up[up[node][i-1]][i-1];
- for(auto p : g[node]) if(p.first!=parent) {
- dist[p.first] = dist[node] + p.second;
- DFS(p.first, node);
- }
- tout[node] = timer++;
- };
- DFS(1, 1);
- auto isAncestor = [=] (int u, int v) {
- return tin[u] <= tin[v] && tout[u] >= tout[v];
- };
- auto getLCA = [=] (int u, int v) {
- if(isAncestor(u, v)) return u;
- if(isAncestor(v, u)) return v;
- for(int i=l; i>=0; --i) if(!isAncestor(up[u][i], v)) {
- u = up[u][i];
- }
- return up[u][0];
- };
- int q; cin >> q;
- while(q--) {
- int u, v; cin >> u >> v;
- cout << dist[u] + dist[v] - 2 * dist[getLCA(u, v)] << '\n';
- }
- #ifndef ONLINE_JUDGE
- cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
- #endif
- }
- int main() {
- ios_base::sync_with_stdio(0);
- cin.tie(0);
- cout.tie(0);
- #ifndef ONLINE_JUDGE
- freopen("input.txt", "r", stdin);
- #endif
- PlayGround();
- return 0;
- }
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