// Author: 4uckd3v - Nguyen Cao Duc
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> ii;
const int MAX_N = 2e5;
const int MAX_K = 1e6;
const int MOD = 1e9 + 7;
const int INF = 1e9;
int n, k, currentCentroid;
int cnt[MAX_K + 5], sz[MAX_N + 5], root[MAX_N + 5];
int res = INF;
bool del[MAX_N + 5];
vector<ii> adj[MAX_N + 5];
void dfs(int u, int par) {
sz[u] = 1;
for (ii e : adj[u]) {
int v = e.first;
if (v == par || del[v]) continue;
dfs(v, u);
sz[u] += sz[v];
};
};
int getCentroid(int u, int par, int n) {
for (ii e : adj[u]) {
int v = e.first;
if (v == par || del[v]) continue;
if (sz[v] * 2 > n)
return getCentroid(v, u, n);
};
return u;
};
void update(int u, int par, bool updateResult, int sum, int d) {
if (sum > k) return;
if (updateResult) {
root[u] = currentCentroid;
res = min(res, d + cnt[k - sum]);
} else {
if (currentCentroid != root[u]) cnt[sum] = INF;
cnt[sum] = min(cnt[sum], d);
};
for (ii e : adj[u]) {
int v = e.first, w = e.second;
if (v == par || del[v]) continue;
update(v, u, updateResult, sum + w, d + 1);
};
};
void decompose(int u, int par) {
dfs(u, par);
int n = sz[u];
int centroid = getCentroid(u, par, n);
del[centroid] = true;
root[centroid] = centroid;
currentCentroid = centroid;
for (ii e : adj[centroid]) {
int v = e.first, w = e.second;
if (del[v]) continue;
update(v, centroid, true, w, 1);
update(v, centroid, false, w, 1);
};
for (ii e : adj[centroid]) {
int v = e.first;
if (del[v]) continue;
decompose(v, centroid);
};
};
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
if (fopen("MAIN.INP", "r")) {
freopen("MAIN.INP", "r", stdin);
freopen("MAIN.OUT", "w", stdout);
};
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));
};
for (int i = 1; i <= k; i++) cnt[i] = INF;
cnt[0] = 0;
decompose(1, 0);
cout << (res == INF ? -1 : res) << '\n';
};
Compilation message
race.cpp: In function 'int main()':
race.cpp:84:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
84 | freopen("MAIN.INP", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
race.cpp:85:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
85 | freopen("MAIN.OUT", "w", stdout);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/ld: /tmp/ccYvkTcU.o: in function `main':
race.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccQjsoXW.o:grader.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/ccQjsoXW.o: in function `main':
grader.cpp:(.text.startup+0x28): undefined reference to `best_path(int, int, int (*) [2], int*)'
collect2: error: ld returned 1 exit status
