#include "traffic.h"
#include <bits/stdc++.h>
using namespace std;
const int NB = 1e6+1;
vector<int> subtree(NB);
vector<bool> vu(NB);
vector<int> ans(NB);
void dfs1(int node, vector<vector<int>>& adj, int pp[]){
int sum = pp[node];
for (int i:adj[node]){
if (!vu[i]){
vu[i] = true;
dfs1(i,adj,pp);
sum += subtree[i];
}
}
subtree[node] = sum;
}
void dfs2(int node, vector<vector<int>>& adj){
for (int i:adj[node]) ans[node] = max(ans[node],subtree[i]);
for (int i:adj[node]){
if (!vu[i]){
vu[i] = true;
int a = subtree[node], b = subtree[i];
subtree[node] -= subtree[i];
subtree[i] += subtree[node];
dfs2(i,adj);
subtree[node] = a;
subtree[i] = b;
}
}
}
int LocateCentre(int N, int pp[], int S[], int D[]) {
subtree = vector<int>(N);
vu = vector<bool>(N);
ans = vector<int>(N);
vector<vector<int>> adj(N);
for (int i=0; i<N-1; ++i){
adj[S[i]].emplace_back(D[i]);
adj[D[i]].emplace_back(S[i]);
}
vu[0] = true;
dfs1(0,adj,pp);
vu = vector<bool>(N);
vu[0] = true;
dfs2(0,adj);
int mini = INT_MAX,idx=0;
for (int i=0; i<N; ++i){
if (mini > ans[i]){
mini = ans[i];
idx = i;
}
}
return idx;
}
