19 lines
686 B
C++
19 lines
686 B
C++
namespace lca {
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int d[MX], L[MX][20];
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void dfs(vector<int> * G, int u = 1, int p = 0) {
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d[u] = d[p] + 1, L[u][0] = p;
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for (int i = 0; i < 18 && L[u][i]; i++) L[u][i + 1] = L[L[u][i]][i];
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for (auto& v : G[u]) if (v != p) dfs(G, v, u);
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}
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int lca(vector<int> * G, int u, int v) {
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if (d[u] > d[v]) swap(u, v);
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for (int i = 18; i >= 0; --i) if (d[v] - (1 << i) >= d[u]) v = L[v][i];
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if (u == v) return u;
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for (int i = 18; i >= 0; --i) if (L[u][i] && L[u][i] != L[v][i]) u = L[u][i], v = L[v][i];
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return L[u][0];
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}
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inline int dist(vector<int> * G, int u, int v) {
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return d[u]+d[v]-2*d[lca(G, u, v)];
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}
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}
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