#include "race.h" #include <bits/stdc++.h> using namespace std; typedef long long ll; const int MAXN = 2e5+7; const int MAXL = 1e6+7; const int INF = 1e8+7; struct Node{ int to, w; }; vector<vector<Node>> graph(MAXN,vector<Node>()); vector<bool> is_off(MAXN,false); vector<int> sub_size(MAXN); vector<pair<int, int>> minNodes(MAXL,{0, -1}); int res=MAXN; void GetSubSizes(int v, int p){ sub_size[v]=1; for(auto [u,w] : graph[v]){ if(is_off[u] || u==p) continue; GetSubSizes(u,v); sub_size[v] += sub_size[u]; } } int FindCentroid(int v, int p, int tree_size){ for(auto [u,_] : graph[v]){ if(is_off[u] || u==p) continue; if(sub_size[u] > ((tree_size+1)/2)) return FindCentroid(u,v,tree_size); } return v; } void ResultDFS(int v, int p, int depth, int val, int k, int c){ if(val > k) return; if (minNodes[k-val].second == c) res = res = min(res, minNodes[k-val].first+depth); for(auto [u,w] : graph[v]){ if(is_off[u] || u==p) continue; ResultDFS(u,v,depth+1,val+w,k,c); } } void UpdateDFS(int v, int p, int depth, int val, int k, int c){ if(val > k) return; if (minNodes[val].second == c) minNodes[val] = min(minNodes[val], {depth, c}); else minNodes[val] = {depth, c}; for(auto [u,w] : graph[v]){ if(is_off[u] || u==p) continue; UpdateDFS(u,v,depth+1,val+w,k,c); } } void ProcessCentroid(int centroid, int k){ minNodes[0]={0, centroid}; for(auto [u,w] : graph[centroid]){ if(is_off[u]) continue; ResultDFS(u,centroid,1,w,k,centroid); UpdateDFS(u,centroid,1,w,k,centroid); } } void CentroidDecomposition(int v, int k){ GetSubSizes(v,v); int centroid = FindCentroid(v,v,sub_size[v]); ProcessCentroid(centroid,k); is_off[centroid]=true; for(auto [u,_] : graph[centroid]){ if(is_off[u]) continue; CentroidDecomposition(u,k); } } int best_path(int N, int K, int H[][2], int L[]) { int n=N, k = K; for(int i=0; i<n-1; ++i) { int nodeA = H[i][0], nodeB = H[i][1], weight = L[i]; graph[nodeA].push_back({nodeB,weight}); graph[nodeB].push_back({nodeA,weight}); } CentroidDecomposition(0,k); if(res==MAXN) res=-1; return res; }