Submission #757760

#	Time	Username	Problem	Language	Result	Execution time	Memory
757760		taher	Dreaming (IOI13_dreaming)	C++17	59 / 100	1079 ms	9568 KiB

dreaming

#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
#include "dreaming.h"

using namespace std;

const int maxN = (int) 1e5 + 1;
vector<pair<int,int>> adj[maxN];
int cnt = 0, n, m, l,sz = 0, ans = 0;
bool vis[maxN];
int parent[maxN];
pair<int, int> p[maxN];

void init() {
  memset(parent, -1, sizeof(parent));
}

pair<int, int> bfs(int node) {
  sz = 0;
  bool seen[n];
  int depth[n];
  memset(seen, 0, sizeof(seen));
  memset(depth, 0, sizeof(depth));
  int best_node = node, best_dist = 0;
  depth[node] = 0;
  seen[node] = true; vis[node] = true;
  queue<int> qs;
  qs.emplace(node);
  while(!qs.empty()) {
    auto f = qs.front();
    sz++;
    if (depth[f] > best_dist) {
      best_dist = depth[f];
      best_node = f;
    }
    qs.pop();
    for (auto x : adj[f]) {
      if (seen[x.first]) continue;
      vis[x.first] = true;
      qs.emplace(x.first);
      parent[x.first] = f;
      depth[x.first] = x.second + depth[f];
      seen[x.first] = true;
    }
  }
  return make_pair(best_node, best_dist);
}

int Get_total(int node) {
  auto val = bfs(node);
  auto f = bfs(val.first);
  return f.second;
}

void Do(int node) {
  auto val = bfs(node);
  if (sz == 1) {
    p[cnt++] = make_pair(0, node);
    return ;
  }
  auto Tke = bfs(val.first);
  parent[val.first] = -1;
  int cur = Tke.first;
  vector<int> path, len;
  while(cur != -1) {
    int nxt = parent[cur];
    path.emplace_back(cur);
    if (nxt == -1) break;
    auto q = lower_bound(adj[cur].begin(), adj[cur].end(), make_pair(nxt, 0));
    len.emplace_back((*q).second);
    cur = parent[cur];    
  }
  int Max = (int)1e9, best_node = -1, s = 0;
  for (int i = 0; i < (int)path.size(); i++) {
    if (i > 0) s += len[i - 1];
    int now_max = max(s, Tke.second - s);
    if (now_max < Max) {
      Max = now_max;
      best_node = path[i];
    }
  }
  ans = max(ans, Tke.second);
  assert(best_node != -1);
  p[cnt++] = make_pair(Max, best_node);
  return ;
}

void make() {
  for (int i = 0; i < n; i++) {
    if (vis[i]) continue;
    Do(i);
    vis[i] = true;
  }
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
  n = N;
  m = M;
  l = L;
  init();

  for (int i = 0; i < m; i++) {
    adj[A[i]].emplace_back(B[i], T[i]);
    adj[B[i]].emplace_back(A[i], T[i]);
  }

  for (int i = 0; i < n; i++) {
    sort(adj[i].begin(),adj[i].end());
  }

  make();

  sort(p, p + n);
  if (cnt >= 2) {
    ans = max(ans, p[n - 1].first + p[n - 2].first + l);
  }
  if (cnt >= 3) {
    ans = max(ans, p[n - 2].first + p[n - 3].first + 2 * l);
  }
  return ans;
}

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