Submission #998340

#	Time	Username	Problem	Language	Result	Execution time	Memory
998340		Nailuj_217	Race (IOI11_race)	C++17	0 / 100	3 ms	13660 KiB

race

#include <bits/stdc++.h>
#define l long long
using namespace std;


#ifdef EVAL
#include "race.h"
#else
#include "grader.cpp"
#endif

const l LEN = 300005;

array<vector<pair<l, l>>, LEN> adj;
array<bool, LEN> processed;
array<l, LEN> subset;

l best;

l subsetsize(l n, l p = -1) {
  l sum = 1;
  for (auto [a, b]: adj[n]) {
    if (!processed[a] && a != p) sum += subsetsize(a, n);
  }
  return subset[n] = sum;
}

l find_centroid(l n, l s, l p = -1) {
  for (auto [a, b]: adj[n]) {
    if (subset[a]*2 > s && a != p && !processed[a]) return find_centroid(a, s, n);
  }
  return n;
}

void explore_branch(l n, map<l, l>* branch, l k, l maxk, l c = 1, l p = -1) {
  if (k > maxk) return;


  if (branch->find(k) != branch->end()) (*branch)[k] = min((*branch)[k], c);
  else branch->insert({k, c}); 


  for (auto [a, b]: adj[n]) {
    if (processed[a] || a == p) continue;
    explore_branch(a, branch, k+b, maxk, c+1, n);
  }
    
    return;
}



l central_decomposition(l n, l k) {
  l centroid = find_centroid(n, subsetsize(n));
  processed[centroid] = true;

  // try unordered if performance problems

  map<l, l> full;
  map<l, l> branch;

  for (auto [a, b]: adj[centroid]) {
    if (processed[a]) continue;

    explore_branch(a, &branch, b, k);

    if (branch.size() > full.size()) swap(branch, full);

    for (auto [key, val]: branch) {
      if (key > k) continue;
      if (key == k) best = min(best, val);
      else if (full.find(k-key) != full.end()) best = min(best, val + full[k-key]);
    }
    
    full.merge(branch);
    branch.clear();

  }


  for (auto [a, b]: adj[centroid])
    if (!processed[a])
      central_decomposition(a, k);

  return best;

}





int best_path(int N, int K, int H[][2], int L[]) {

  if (N == 1) return -1;


  adj.fill({});
  processed.fill(0);
  best = 1LL<<60;

  for (int i = 0; i < N-1; i++) {
    adj[H[i][0]].push_back({H[i][1], L[i]});
    adj[H[i][1]].push_back({H[i][0], L[i]});
  }

  central_decomposition(1, K);



  if (best == (1LL<<60)) return -1;
  return best;
}

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