# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
373948 | duchung | Race (IOI11_race) | C++17 | 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.
#define ii pair<int , int>
#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int n , k , ans = 1e9;
int dist[N] , depth[N];
vector<ii> adj[N];
set<ii> S[N];
void dfs(int u , int p = -1)
{
S[u].insert(make_pair(dist[u] , depth[u]));
for (auto e : adj[u])
{
int v = e.first;
int w = e.second;
if (v == p) continue;
dist[v] = dist[u] + w;
depth[v] = depth[u] + 1;
dfs(v , u);
if (S[u].size() < S[v].size()) swap(S[u] , S[v]);
for (auto x : S[v])
{
auto it = S[u].lower_bound(make_pair(k - x.first + 2 * dist[u] , 0));
if (it != S[u].end() && it->first + x.first - 2 * dist[u] == k) ans = min(ans , it->second + x.second - 2 * depth[u]);
}
for (auto x : S[v])
{
S[u].insert(x);
}
}
}
int main()
{
// freopen(".inp","r",stdin);
// freopen(".out","w",stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> k;
for (int i = 1 ; i < n ; ++i)
{
int u , v , w;
cin >> u >> v >> w;
++u ; ++v;
adj[u].push_back(ii(v , w));
adj[v].push_back(ii(u , w));
}
dfs(1);
cout << (ans == 1e9 ? -1 : ans);
}