56 lines
1.8 KiB
C++
56 lines
1.8 KiB
C++
// BUG: unchecked code
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struct virtual_tree {
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int n, root;
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vector<vector<pil>> e;
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LCA lca;
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vector<int> dfn;
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vector<ll> ps;
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virtual_tree(const vector<vector<pil>>& e, int root) : n(e.size() - 1), root(root), e(e), lca(vector<vector<int>> {{}, {}}), dfn(n + 1), ps(n + 1) {
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vector<vector<int>> ch(n + 1);
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for (int u = 0; u <= n; ++u) {
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for (auto&& [v, w] : e[u]) {
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ch[u].emplace_back(v);
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}
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}
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lca = LCA(ch);
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int t = 0;
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auto dfs = [&] (auto dfs, int v, int pa) -> void {
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dfn[v] = ++t;
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for (auto&& [u, w] : e[v]) {
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if (u == pa) continue;
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ps[u] = ps[v] + w;
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dfs(dfs, u, v);
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}
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};
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dfs(dfs, root, 0);
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}
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// vertex number starts from 0
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pair<vector<vector<pil>>, vector<int>> generate(vector<int> pivots) {
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int m = pivots.size();
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if (m == 0) return {};
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sort_by_key(pivots.begin(), pivots.end(), expr(dfn[v], int v));
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vector<int> a;
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for (int i = 0; i < m - 1; ++i) {
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int v = pivots[i];
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int u = lca.query(pivots[i], pivots[i + 1]);
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a.emplace_back(v);
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a.emplace_back(u);
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}
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a.emplace_back(pivots[m - 1]);
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sort_by_key(a.begin(), a.end(), expr(dfn[v], int v));
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m = unique(a.begin(), a.end()) - a.begin();
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unordered_map<int, int, safe_hash> mp;
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vector<int> rev(m);
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for (int i = 0; i < m; ++i) {
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mp[a[i]] = i;
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rev[i] = a[i];
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}
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vector<vector<pil>> ret(m);
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for (int i = 0; i < m - 1; ++i) {
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int l = lca.query(a[i], a[i + 1]);
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edgew(ret, mp[l], i + 1, ps[a[i + 1]] - ps[l]);
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}
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return { ret, rev };
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}
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};
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