# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
1140914 | why1 | Race (IOI11_race) | C++20 | 0 ms | 0 KiB |
#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define pii pair<int,int>
#define fi first
#define se second
#define sz size()
#define pb push_back
const int N = 2e5;
int n,k;
int h[N+1][2],l[N+1];
vector<pii> g[N+1];
int dw[N+1],d[N+1];
set<pii> st[N+1];
int ans=1e9;
void calc(int v,int pr){
for(auto [to,i]: g[v]){
if(to!=pr){
dw[to]=dw[v]+l[i];
d[to]=d[v]+1;
calc(to,v);
}
}
}
void dfs(int v,int pr){
st[v].insert({dw[v],v});
for(auto [to,i]: g[v]){
if(to!=pr){
dfs(to,v);
if(st[v].sz<st[to].sz)
st[v].swap(st[to]);
for(auto [D,j]: st[to]){
int x=k+2*dw[v]-D;
auto it=st[v].lower_bound({x,0});
if(it!=st[v].end() && it->fi==x){
ans=min(ans,d[j]+d[it->se]-2*d[v]);
}
}
for(auto j: st[to]){
st[v].insert(j);
}
}
}
}
int best_path(int n, int k, int h[][2], int l[])
//void solve(){
cin>>n>>k;
for(int i = 1; i <= n-1; i++){
cin>>h[i][0]>>h[i][1]>>l[i];
h[i][0]++,h[i][1]++;
g[h[i][0]].pb({h[i][1],i});
g[h[i][1]].pb({h[i][0],i});
}
calc(1,-1);
dfs(1,-1);
/*
for(int i = 1; i <= n; i++){
cout<<i<<": ";
for(auto j: st[i]){
cout<<"{"<<j.fi<<" "<<j.se<<"} ";
}
cout<<"\n";
}
cout<<ans<<"\n";
*/
return ans;
}
/*
int main(){
solve();
return 0;
}
*/