17 lines
489 B
C++
17 lines
489 B
C++
int d[200005], L[200005][20];
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vector<int> G[200005];
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void dfs(int u, int p) {
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d[u] = d[p] + 1;
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L[u][0] = p;
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for (int i = 0; i < 16 && 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(v, u);
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}
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int lca(int u, int v) {
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if (d[u] > d[v]) swap(u, v);
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for (int i = 16; 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 = 16; 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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} |