Create lca.cpp
This commit is contained in:
parent
eb4a3157f3
commit
c9b31c10c2
1 changed files with 17 additions and 0 deletions
17
Graph/lca.cpp
Normal file
17
Graph/lca.cpp
Normal file
|
@ -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];
|
||||
}
|
Loading…
Reference in a new issue