| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 865541 | tamir1 | Race (IOI11_race) | C++98 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include<bits/stdc++.h>
#define ll int
#define pp pair<ll,ll>
#define f first
#define s second
using namespace std;
ll N,K,L[200001],i,a,b,ans=200010,sz[200001],H[200001][2];
bitset<200001> mark;
map<ll,ll> mp;
vector<pp> G[200001];
ll getsize(ll a,ll p=-1){
sz[a]=1;
for(pp i:G[a]){
if(p!=i.f && !mark[i.f])
sz[a]+=getsize(i.f,a);
}
return sz[a];
}
ll centroid(ll a,ll p,ll n){
for(pp i:G[a]){
if(p!=i.f && sz[i.f]>n/2 && !mark[i.f])
return centroid(i.f,a,n);
}
return a;
}
void dfs(ll a,ll p,ll dist,ll len,bool key){
if(dist>K) return;
if(dist==K){
ans=min(ans,len);
return;
}
if(key){
if(mp[K-dist])
ans=min(ans,len+mp[K-dist]);
}
else{
if(!mp[dist]) mp[dist]=len;
else mp[dist]=min(mp[dist],len);
}
for(pp i:G[a]){
if(p!=i.f && !mark[i.f]){
dfs(i.f,a,dist+i.s,len+1,key);
}
}
}
void solve(ll a){
ll n,cnt;
n=getsize(a);
cnt=centroid(a,0,n);
mark[cnt]=1;
mp.clear();
for(pp i:G[cnt]){
if(!mark[i.f]){
dfs(i.f,cnt,i.s,1,1);
dfs(i.f,cnt,i.s,1,0);
}
}
for(pp i:G[cnt]){
if(!mark[i.f])
solve(i.f);
}
}
ll best_path(ll N,ll K,ll H[][2],ll L[]){
for(i=1;i<N;i++){
a=H[i][0]+1;
b=H[i][1]+1;
G[a].push_back({b,L[i]});
G[b].push_back({a,L[i]});
}
solve(1);
if(ans==200010) return -1;
return ans;
}
ll cur;
main(){
cin >> N >> K;
for(i=1;i<N;i++){
cin >> H[i][0] >> H[i][1] >> L[i];
}
cur=best_path(N,K,H,L);
cout << cur;
}