#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long int
const int INF = 1000000000;
int flagAtual = 1;
vector<pair<int, int>> melhor;
vector<bool> block;
vector<pair<int, ll>> edges_dist;
// Resposta.
int menor_K = INF;
// calcula o tamanho da subarvore
void get_SubTreeSize(vector<vector<pair<int,int>>> &adj, vector<int> &subtreeSz, int v, int pai) {
subtreeSz[v] = 1;
for (auto& [u, val] : adj[v]) {
if (u == pai || block[u]) continue;
get_SubTreeSize(adj, subtreeSz, u, v);
subtreeSz[v] += subtreeSz[u];
}
}
// percorre todos os vertices e retorna o centroide...
int findCentroid(vector<vector<pair<int,int>>> &adj, vector<int> &subtreeSz, int v, int pai, int size) {
for (auto& [chi, val] : adj[v])
if (chi != pai && !block[chi] && subtreeSz[chi] * 2 > size)
return findCentroid(adj, subtreeSz, chi, v, size);
return v;
}
void dfs1(vector<vector<pair<int,int>>> &adj, int v, int pai, ll dist, int total, int K) {
if (dist > K) return;
edges_dist[v] = { total, dist };
int idx = (int)(K - dist);
int aux = (melhor[idx].second == flagAtual) ? melhor[idx].first : INF;
if (aux + total < menor_K)
menor_K = aux + total;
for (auto& [ch, val] : adj[v])
if (ch != pai && !block[ch])
dfs1(adj, ch, v, dist + (ll)val, total + 1, K);
}
void dfs2(vector<vector<pair<int,int>>> &adj, int v, int pai, int K) {
int edges = edges_dist[v].first;
ll dist_ll = edges_dist[v].second;
if (dist_ll > K) return;
int idx = (int)dist_ll;
if (melhor[idx].second != flagAtual || melhor[idx].first > edges) {
melhor[idx].first = edges;
melhor[idx].second = flagAtual;
}
for (auto& [ch, val] : adj[v])
if (!block[ch] && ch != pai)
dfs2(adj, ch, v, K);
}
int best_path(int N, int K, int H[][2], int L[]) {
vector<vector<pair<int,int>>> adj(N);
vector<int> subtreeSz(N);
melhor.assign(K+1, {INF, 0});
block.assign(N, false);
edges_dist.assign(N, {-1, -1LL});
menor_K = INF;
flagAtual = 1;
for (int i = 0; i < N-1; ++i) {
adj[H[i][0]].push_back({H[i][1], L[i]});
adj[H[i][1]].push_back({H[i][0], L[i]});
}
queue<int> Q;
Q.push(0);
while (!Q.empty()) {
int node = Q.front(); Q.pop();
if (block[node]) continue;
get_SubTreeSize(adj, subtreeSz, node, -1);
int cent = findCentroid(adj, subtreeSz, node, -1, subtreeSz[node]);
block[cent] = true;
melhor[0] = {0, flagAtual};
for (auto& [ch, val] : adj[cent]) {
if (!block[ch]) {
dfs1(adj, ch, cent, (ll)val, 1, K);
dfs2(adj, ch, cent, K);
Q.push(ch);
}
}
flagAtual++;
}
if (menor_K == INF) return -1;
return menor_K;
}
