| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 676715 | d4xn | 경주 (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.
#pragma GCC optimize ("Ofast")
#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 2e5+1, inf = LLONG_MAX;
int n, k, sz[N];
ll ans;
vector<pair<int, ll>> adj[N];
bitset<N> r;
void dfs(int u, int par) {
sz[u] = 1;
for (auto &[v, w] : adj[u]) {
if (v == par || r[v]) continue;
dfs(v, u);
sz[u] += sz[v];
}
}
int find_centroid(int u, int par, int rt) {
for (auto &[v, w] : adj[u]) {
if (v != par && !r[v] && sz[v] > sz[rt]/2) {
return find_centroid(v, u, rt);
}
}
return u;
}
void dfs2(int u, int par, int d, ll dw, map<ll, int> &dis) {
if (dw > k || d >= ans) return;
auto it = dis.find(dw);
if (it == dis.end()) dis[dw] = d;
else it->second = min(it->second, d);
for (auto &[v, w] : adj[u]) {
if (v == par || r[v]) continue;
dfs2(v, u, d+1, dw+w, dis);
}
}
void solve_centroid(int u) {
map<ll, int> mnD;
mnD[0] = 0;
for (auto &[v, w] : adj[u]) {
if (r[v]) continue;
map<ll, int> mnD2;
dfs2(v, u, 1, w, mnD2);
if (mnD2.size() > mnD.size()) swap(mnD, mnD2);
for (auto &[dw, d] : mnD2) {
auto it = mnD.find(k-dw);
if (it == mnD.end()) break;
ans = min(ans, d+it->second);
}
for (auto &[dw, d] : mnD2) {
auto it = mnD.find(dw);
if (it == mnD.end()) mnD[dw] = d;
else it->second = min(it->second, d);
}
}
}
void dec(int u) {
dfs(u, u);
int ct = find_centroid(u, u, u);
r[ct] = 1;
solve_centroid(ct);
for (auto &[v, w] : adj[ct]) {
if (r[v]) continue;
dec(v);
}
}
int best_path(int N, int K, int H[][2], int L[]) {
ans = inf;
n = N;
k = K;
for (int i = 0; i < n-1; i++) {
adj[H[i][0]].push_back(make_pair(H[i][1], L[i]));
adj[H[i][1]].push_back(make_pair(H[i][0], L[i]));
}
dec(0);
return (ans == inf ? -1 : ans);
}