51 lines
1.3 KiB
Lua
51 lines
1.3 KiB
Lua
|
return [=[
|
||
|
|
struct LCA {
|
||
|
|
vector<int> depth;
|
||
|
|
vector<vector<int>> pa;
|
||
|
|
LCA(const vector<vector<int>>& g, int root = 1) {
|
||
|
|
int n = g.size() - 1;
|
||
|
|
int m = 32 - __builtin_clz(n);
|
||
|
|
depth.resize(n + 1);
|
||
|
|
pa.resize(n + 1, vector<int>(m, -1));
|
||
|
|
function<void(int, int)> dfs = [&](int x, int fa) {
|
||
|
|
pa[x][0] = fa;
|
||
|
|
for (int y: g[x]) {
|
||
|
|
if (y != fa) {
|
||
|
|
depth[y] = depth[x] + 1;
|
||
|
|
dfs(y, x);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
};
|
||
|
|
dfs(root, 0);
|
||
|
|
|
||
|
|
for (int i = 0; i < m - 1; i++)
|
||
|
|
for (int x = 1; x <= n; x++)
|
||
|
|
if (int p = pa[x][i]; p != -1)
|
||
|
|
pa[x][i + 1] = pa[p][i];
|
||
|
|
}
|
||
|
|
|
||
|
|
int get_kth_ancestor(int node, int k) {
|
||
|
|
for (; k; k &= k - 1)
|
||
|
|
node = pa[node][__builtin_ctz(k)];
|
||
|
|
return node;
|
||
|
|
}
|
||
|
|
|
||
|
|
int query(int x, int y) {
|
||
|
|
if (depth[x] > depth[y])
|
||
|
|
swap(x, y);
|
||
|
|
y = get_kth_ancestor(y, depth[y] - depth[x]);
|
||
|
|
if (y == x)
|
||
|
|
return x;
|
||
|
|
for (int i = pa[x].size() - 1; i >= 0; i--) {
|
||
|
|
int px = pa[x][i], py = pa[y][i];
|
||
|
|
if (px != py) {
|
||
|
|
x = px;
|
||
|
|
y = py;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return pa[x][0];
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
]=]
|