Create lca.cpp

Changes

1 changed files (+17/-0)

• Graph/lca.cpp (new)
  • @@ -0,0 +1,17 @@
    + int d[50005] = { 0 }, L[20][50005] = { 0 }; + vector<int> G[50005]; + + void dfs(int u, int p) { + d[u] = d[p] + 1; + L[0][u] = p; + for (int i = 0; (1 << i) < N; i++) if (L[i][u]) L[i + 1][u] = L[i][L[i][u]]; + for (int v : G[u]) if (v != p) dfs(v, u); + } + + int lca(int u, int v) { + if (d[u] > d[v]) swap(u, v); + for (int i = log2(N); i >= 0; i--) if (d[v] - (1 << i) >= d[u]) v = L[i][v]; + if (u == v) return u; + for (int i = log2(N); i >= 0; i--) if (L[i][u] && L[i][u] != L[i][v]) u = L[i][u], v = L[i][v]; + return L[0][u]; + }