#include "migrations.h"
#include <bits/stdc++.h>
using namespace std;
using pi = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vi>;
void dfs(int u, int p, vi &dist, vvi &adj) {
for (auto &v : adj[u]) {
if (v == p) continue;
dist[v] = dist[u] + 1;
dfs(v, u, dist, adj);
}
}
int furthest_from(int u, int n, vvi &adj) {
vector<int> dist(n);
dfs(u, u, dist, adj);
int f = 0; for (int i = 0; i < n; i++) if (dist[i] > dist[f]) f = i;
return f;
}
vvi adj;
int send_message(int n, int i, int Pi) {
if (i <= 1) adj.assign(n+1, vi());
adj[Pi].push_back(i);
adj[i].push_back(Pi);
if (i >= n - 18) {
int furthest = furthest_from(0, n, adj);
int bit = i - (n - 18);
if (furthest == i) {
return 2;
} else {
return (furthest & (1 << bit)) ? 1 : 0;
}
}
return 0;
}
pi longest_path(vi S) {
int n = S.size();
int pf = 0;
for (int i = max(0, n - 18); i < n; i++) if (S[i] == 2) pf = i;
if (pf != 0) return {0, pf};
for (int i = n - 18; i < n; i++) {
pf += S[i] << (i - (n - 18));
}
return {0, pf};
}
