#include "race.h"
#include <vector>
#include <map>
#include <functional>
#include <iostream>
using namespace std;
void merge(map<int, int> &a, map<int, int> &b, int l)
{
if (a.size() < b.size())
swap(a, b);
for (auto [nk, v] : b)
{
int k = nk - l;
if (a.find(k) != a.end())
a[k] = min(a[k], v + 1);
else
a[k] = v + 1;
}
}
int best_path(int n, int k, int h[][2], int l[])
{
cout << "CALLING best_path(" << n << ", " << k << ", {";
vector<vector<pair<int, int>>> g(n);
for (int i = 0; i < n - 1; i++)
{
int u = h[i][0], v = h[i][1];
u--, v--;
g[u].push_back({v, l[i]});
g[v].push_back({u, l[i]});
}
vector<map<int, int>> paths(n);
for (int i = 0; i < n; i++)
paths[i][k] = 0;
int minPaths = n + 1;
function<void(int, int)> dfs = [&](int u, int p)
{
for (auto [v, w] : g[u])
{
if (v == p)
continue;
dfs(v, u);
merge(paths[u], paths[v], w);
}
if (paths[u].find(0) != paths[u].end())
minPaths = min(minPaths, paths[u][0]);
};
dfs(0, -1);
return minPaths == n + 1 ? -1 : minPaths;
}
