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 <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int n,k;
bool used[200002], used_1[200002], used_2[200002];
vector<pair<int,int>>g[200002];
int size[200002];
int tree_centroid;
int best[200002];
const int inf = 1e9;
int ans = 1e9;
void dfs(int node, int dad = -1)
{
size[node] = 1;
for (auto it : g[node])
if (!used[it.first] && it.first != dad)
{
dfs(it.first, node);
size[node] += size[it.first];
}
}
void findcentroid(int v, int flo){
used_1[v]=true;
int zib=0;
for(auto x:g[v]){
if(used_1[x.first])continue;
if(size[x.first] - 1 >= flo){
zib++;
findcentroid(x.first, flo);
break;
}
}
if(zib==0)
tree_centroid=v;
}
void dfs2(int x, int p, int cost, int l, vector<pair<int,int>>&to_ans) {
if (cost <= k)
to_ans.push_back(make_pair(cost, l));
for (auto y : g[x]) {
if (used_2[y.first] || y.first == p)continue;
dfs2(y.first, x, cost + y.second, l + 1, to_ans);
}
}
int solve(int node) {
dfs(node);
fill(used_1, used_1 + 200002, false);
int zibil = size[node] - 1;
findcentroid(node, zibil / 2);
node = tree_centroid;
best[0] = 0;
vector<int>del;
vector<pair<int, int>>to_ans;
for (auto x : g[node]) {
int son = x.first;
if (used_2[son])continue;
to_ans.clear();
dfs2(x.first, node, x.second, 1, to_ans);
for (auto it : to_ans)
ans = min(ans, it.second + best[k - it.first]);
for (auto it : to_ans)
{
best[it.first] = min(best[it.first], it.second);
del.push_back(it.first);
}
}
for (auto it : del)
best[it] = inf;
used_2[node] = true;
for (auto it : g[node])
if (!used_2[it.first])
ans = min(ans, solve(it.first));
return ans;
}
int best_path(int N, int _K, int H[][2], int L[])
{
k = _K;
int i;
for(i=0; i<N-1; ++i)
{
int x, y, z;
x = H[i][0];
y = H[i][1];
z = L[i];
g[x].push_back(make_pair(y,z));
g[y].push_back(make_pair(x,z));
}
for(i=0; i<=k; ++i) best[i] = inf;
int X = solve(0);
if(X == inf) return -1;
return X;
}
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