Submission #940970

#	Time	Username	Problem	Language	Result	Execution time	Memory
940970		duckindog	Dreaming (IOI13_dreaming)	C++17	0 / 100	1048 ms	15052 KiB

dreaming

#include <bits/stdc++.h>

using namespace std;

#ifndef LOCAL
#include "dreaming.h"
#endif

const int N = 100'000 + 10;
vector<pair<int, int>> ad[N];

int f[N], trace[N];
bool mk[N];
vector<int> node;
void dfs(int u, int p = -1) { 
  mk[u] = true;
  node.push_back(u);
  trace[u] = p;
  for (const auto& [v, w] : ad[u]) { 
    if (v == p) continue;
    f[v] = f[u] + w;
    dfs(v, u);
  }
}

pair<int, int> findMid(int u) { 
  int v = u;
  for (int t = 0; t < 2; ++t) { 
    for (const auto& x : node) f[x] = 0;
    node.clear();
    dfs(u);
    for (const auto& x : node) if (f[v] < f[x]) v = x;
    u = v;
  }
  int ret = v;
  while (v != -1) { 
    if (max(f[v], f[u] - f[v]) < max(f[ret], f[u] - f[ret])) ret = v;
    v = trace[v];
  }
  return {max(f[ret], f[u] - f[ret]), ret};
}

void tree(int u, int p = -1) { 
  for (const auto& [v, w] : ad[u]) { 
    if (v == p) continue;
    cout << u << " " << v << " " << w << "\n";
    tree(v, u);
  }
}

int travelTime(int n, int m, int l, int A[],int B[],int T[]) { 
  for (int i = 1; i <= m; ++i) { 
    int u = A[i], v = B[i], w = T[i];
    ad[u].push_back({v, w});
    ad[v].push_back({u, w});
  }

  vector<pair<int, int>> mid;
  for (int i = 0; i < n; ++i) { 
    if (mk[i]) continue;
    mid.push_back(findMid(i));
  }
  sort(mid.begin(), mid.end(), greater<>());

  memset(trace, -1, sizeof trace);
  for (const auto& x : mid) { 
    if (x == mid[0]) continue;
    int u = mid[0].second, v = x.second;
    ad[u].push_back({v, l});
    ad[v].push_back({u, l});
  }
  // tree(0);
  memset(f, 0, sizeof f);
  memset(trace, -1, sizeof trace);
  findMid(0);
  
  cerr << 1.0 * clock() / CLOCKS_PER_SEC << "\n";
  return *max_element(f, f + n);
}

#ifdef LOCAL
int n, m, l;
int A[N], B[N], T[N];


mt19937_64 rng(chrono::steady_clock().now().time_since_epoch().count());
int rnd(int l, int r) { return l + rng() % (r - l + 1); }

int id[N];
int root(int u) { return id[u] < 0 ? u : id[u] = root(id[u]); }
void add(int u, int v) { 
  u = root(u); v = root(v);
  if (u == v) return;
  if (id[u] > id[v]) swap(u, v);
  id[u] += id[v];
  id[v] = u;
}

int32_t main() { 
  cin.tie(0)->sync_with_stdio(0);

  // memset(id, -1, sizeof id);
  // n = rnd(1e5, 1e5), m = rnd(0, n - 1), l = rnd(1, 1e4);
  // for (int i = 1; i <= m; ++i) { 
  //   int u = rnd(0, n - 1), v = rnd(u + 1, u + 1);
  //   while (root(u) == root(v)) u = rnd(0, n - 1), v = rnd(u + 1, u + 1);
  //   add(u, v);
  //   A[i] = u; B[i] = v; T[i] = rnd(1, 1e4);
  // }

  cin >> n >> m >> l;
  for (int i = 1; i <= m; ++i) cin >> A[i] >> B[i] >> T[i];
  
  cout << travelTime(n, m, l, A, B, T) << "\n";
}
#endif

• Subtask 1: 0 / 14
• Subtask 2: 0 / 10
• Subtask 3: 0 / 23
• Subtask 4: 0 / 18
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23