# | 제출 시각 | 아이디 | 문제 | 언어 | 결과 | 실행 시간 | 메모리 |
---|---|---|---|---|---|---|---|
1268826 | bgnbvnbv | Race (IOI11_race) | C++20 | 0 ms | 0 KiB |
#include <bits/stdc++.h>
using namespace std;
#define int long long
const int INF = 1e18;
const int MAXN = 200005;
vector<pair<int,int>> adj[MAXN];
int sz[MAXN];
bool removed[MAXN];
int ans;
int N_global, K_global;
int dfs_size(int u,int p){
sz[u] = 1;
for(auto [v,w] : adj[u]){
if(!removed[v] && v != p) sz[u] += dfs_size(v,u);
}
return sz[u];
}
int dfs_cen(int u, int p, int n){
for(auto [v,w] : adj[u]){
if(!removed[v] && v != p){
if(sz[v] > n / 2) return dfs_cen(v,u,n);
}
}
return u;
}
void dfs_collect(int u,int p, long long dist, int d ,vector<pair<long long,int>> &path){
if(dist > K_global) return;
path.push_back({dist,d});
for(auto [v,w] : adj[u]){
if(!removed[v] && v != p){
dfs_collect(v,u,dist+w,d+1,path);
}
}
}
void solve(int root){
int n = dfs_size(root,-1);
int c = dfs_cen(root,-1,n);
unordered_map<long long,int> best;
best[0] = 0;
for(auto [v,w] : adj[c]){
if(removed[v]) continue;
vector<pair<long long,int>> path;
dfs_collect(v,c,w,1,path);
for(auto [dist, d] : path){
if(dist == K_global) ans = min(ans,d);
if(best.count(K_global - dist)){
ans = min(ans,d + best[K_global - dist]);
}
}
for(auto [dist, d] : path){
if(!best.count(dist)) best[dist] = d;
else best[dist] = min(best[dist],d);
}
}
removed[c] = true;
for(auto [v,w] : adj[c]){
if(!removed[v]) solve(v);
}
}
int best_path(int N,int K, vector<vector<int>> H, vector<int> L){
N_global = N; K_global = K;
for(int i=0;i<N;++i){
adj[i].clear();
removed[i] = false;
}
ans = INF;
for(int i=0;i<N-1;++i){
int u = H[i][0], v = H[i][1], w = L[i];
adj[u].push_back({v,w});
adj[v].push_back({u,w});
}
solve(0);
return (ans == INF ? -1 : ans);
}
int32_t main(){
return 0; // không cần gì thêm
}