Submission #592714

#	Time	Username	Problem	Language	Result	Execution time	Memory
592714		ikaurov	Race (IOI11_race)	C++17	43 / 100	290 ms	72896 KiB

race

#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define all(arr) (arr).begin(), (arr).end()
#define ll long long
#define ld long double
#define pb push_back
#define sz(x) int((x).size())
#define fi first
#define se second
#define endl '\n'

const int N = 2e5 + 20, INF = 1e9;

vector<pair<int, int>> g[N];
map<ll, ll> min_edges[N];
ll delta_length[N], delta_cnt[N];
ll ans = INF, K;

void dfs(int v, int p){
  int maxguy = -1, maxw;
  for (auto [u, w] : g[v]){
    if (u == p) continue;
    dfs(u, v);
    if (maxguy == -1 || sz(min_edges[maxguy]) < sz(min_edges[u])) maxguy = u, maxw = w;
  }
  if (maxguy != -1){
    min_edges[v] = move(min_edges[maxguy]), delta_length[v] = delta_length[maxguy] + maxw,
    delta_cnt[v] = delta_cnt[maxguy] + 1;
  }
  for (auto [u, w] : g[v]){
    if (u == p) continue;
    if (u != maxguy){
      for (auto [len, cnt] : min_edges[u]){
        ll len1 = len + delta_length[u] + w - delta_length[v];
        ll cnt1 = cnt + delta_cnt[u] + 1 - delta_cnt[v];
        if (min_edges[v].count(K - len1 - 2 * delta_length[v])){
          ans = min(ans, cnt1 + 2 * delta_cnt[v] + min_edges[v][K - len1 - 2 * delta_length[v]]);
        }
        if (min_edges[v].count(len1)) min_edges[v][len1] = min(min_edges[v][len1], cnt1);
        else min_edges[v][len1] = cnt1;
      }
      min_edges[u].clear();
    }
  }
  min_edges[v][-delta_length[v]] = -delta_cnt[v];
  if (min_edges[v].count(K - delta_length[v])) ans = min(ans, min_edges[v][K - delta_length[v]] + delta_cnt[v]);
}

int best_path(int n, int k, int h[][2], int l[]){
  for (int i = 0; i < n; i++){
    g[i].clear();
    min_edges[i].clear();
    delta_length[i] = delta_cnt[i] = 0;
  }
  K = k, ans = INF;
  for (int i = 0; i < n - 1; i++){
    g[h[i][0]].pb({h[i][1], l[i]});
    g[h[i][1]].pb({h[i][0], l[i]});
  }
  dfs(0, 0);
  return ans == INF? -1 : ans;
}

// signed main(){
//   ios_base::sync_with_stdio(0);
//   cin.tie(0);
//   // cout.precision(20);
//   int n, k;
//   cin >> n >> k;
//   int h[n - 1][2], l[n - 1];
//   for (int i = 0; i < n - 1; i++){
//     cin >> h[i][0] >> h[i][1];
//   }
//   for (int i = 0; i < n - 1; i++){
//     cin >> l[i];
//   }
//   cout << best_path(n, k, h, l) << endl;
// }

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 0 / 57