Function dfs

Trees/LCA.cpp:11–24

vector<vector<int>> up;
 
void dfs(int v, int p)
{
    tin[v] = ++timer;
    up[v][0] = p;
    for (int i = 1; i <= l; ++i)
        up[v][i] = up[up[v][i-1]][i-1];
 
    for (int u : adj[v]) {
        if (u != p)
            dfs(u, v);
    }
 
    tout[v] = ++timer;
}
 
bool is_ancestor(int u, int v)
{