#pragma GCC optimize("O3")
//#include "grader.h"
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define enl printf("\n")
#define case(t) printf("Case #%d: ", (t))
#define ni(n) scanf("%d", &(n))
#define nl(n) scanf("%I64d", &(n))
#define nai(a, n) for (int i = 0; i < (n); i++) ni(a[i])
#define nal(a, n) for (int i = 0; i < (n); i++) nl(a[i])
#define pri(n) printf("%d\n", (n))
#define prl(n) printf("%I64d\n", (n))
#define pii pair<int, int>
#define pll pair<long long, long long>
#define vii vector<pii>
#define vi vector<int>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef cc_hash_table<int,int,hash<int>> ht;
const double pi = acos(-1);
const int MOD = 1e9 + 7;
const int INF = 1e9 + 7;
const int MAXN = 1e6 + 5;
const double eps = 1e-9;
vii adj[MAXN];
int ans = INF, sz[MAXN], vis[MAXN], n, k;
void getSz(int u, int p)
{
sz[u] = 1;
for (pii v: adj[u])
if (v.fi != p && !vis[v.fi])
{
getSz(v.fi, u);
sz[u] += sz[v.fi];
}
}
int findCen(int u, int p, int n)
{
for (pii v: adj[u])
if (v.fi != p && !vis[v.fi] && sz[v.fi] > n / 2)
return findCen(v.fi, u, n);
return u;
}
ht cnt, cnt2;
void add(int u, int p, int d, int w)
{
if (w == k)
ans = min(ans, d);
w = min(w, INF);
if (cnt.find(w) == cnt.end())
cnt[w] = INF;
cnt[w] = min(cnt[w], d);
if (cnt2.find(k - w) != cnt2.end())
ans = min(ans, cnt2[k - w] + d);
for (pii v: adj[u])
if (v.fi != p && !vis[v.fi])
add(v.fi, u, d + 1, w + v.se);
}
void join(int u, int p, int d, int w)
{
w = min(w, INF);
if (cnt2.find(w) == cnt2.end())
cnt2[w] = INF;
cnt2[w] = min(cnt2[w], d);
for (pii v: adj[u])
if (v.fi != p && !vis[v.fi])
join(v.fi, u, d + 1, w + v.se);
}
void decompose(int u)
{
getSz(u, -1);
int c = findCen(u, -1, sz[u]);
vis[c] = 1;
for (pii v: adj[c])
if (!vis[v.fi])
decompose(v.fi);
for (pii v: adj[c])
{
if (vis[v.fi])
continue;
add(v.fi, c, 1, v.se);
join(v.fi, c, 1, v.se);
cnt.clear();
}
cnt2.clear();
vis[c] = 0;
}
/*int best_path(int N, int K, int H[][2], int L[]){
n = N, k = K;
for (int i = 1; i < n; i++)
{
int u = H[i-1][0], v = H[i-1][1], w = L[i-1];
u--, v--;
adj[u].pb({v, w});
adj[v].pb({u, w});
}
decompose(0);
if (ans == INF)
ans = -1;
return ans;
}*/
int main()
{
ni(n), ni(k);
for (int i = 1; i < n; i++)
{
int u, v, w;
ni(u), ni(v), ni(w);
u--, v--;
adj[u].pb({v, w});
adj[v].pb({u, w});
}
decompose(0);
if (ans == INF)
ans = -1;
pri(ans);
return 0;
}
Compilation message
race.cpp: In function 'int main()':
race.cpp:118:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
ni(n), ni(k);
^
race.cpp:118:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
race.cpp:122:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
ni(u), ni(v), ni(w);
^
race.cpp:122:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
race.cpp:122:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
/tmp/ccEsEGPE.o: In function `main':
race.cpp:(.text.startup+0x0): multiple definition of `main'
/tmp/ccQJaWN5.o:grader.cpp:(.text.startup+0x0): first defined here
/tmp/ccQJaWN5.o: In function `main':
grader.cpp:(.text.startup+0x20): undefined reference to `best_path(int, int, int (*) [2], int*)'
collect2: error: ld returned 1 exit status
