Submission #940803

#	Time	Username	Problem	Language	Result	Execution time	Memory
940803		duckindog	Dreaming (IOI13_dreaming)	C++17	0 / 100	1026 ms	16328 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);
  }
}
long long wei[N];
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[x] > f[v]) v = x;
    u = v;
  }
  
  vector<int> path;
  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];
  }
  wei[ret] = max(f[ret], f[u] - f[ret]);
  return ret;
}

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});
  }

  memset(trace, -1, sizeof trace);
  vector<int> nodes;
  for (int i = 0; i < n; ++i) { 
    if (mk[i]) continue;
    nodes.push_back(findMid(i));
  }

  sort(nodes.begin(), nodes.end(), [&](const auto& a, const auto& b) { 
    return wei[a] > wei[b];
  });

  for (const auto& x : nodes) { 
    if (x == nodes[0]) continue;
    ad[x].push_back({nodes[0], l});
    ad[nodes[0]].push_back({x, l});
  }

  memset(f, 0, sizeof f);
  memset(trace, -1, sizeof trace);

  findMid(1);

  return *max_element(f, f + n); 
}

#ifdef LOCAL
int n, m, l;
int A[N], B[N], T[N];
int32_t main() { 
  cin.tie(0)->sync_with_stdio(0);

  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