Submission #376049

#	Time	Username	Problem	Language	Result	Execution time	Memory
376049		WLZ	Dreaming (IOI13_dreaming)	C++14	100 / 100	139 ms	26812 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
using namespace std;

const int INF = 0x3f3f3f3f;

int cur_cc = 0;
vector< vector< pair<int, int> > > g;
vector<int> cc, d, mn, mx, diameter;

void dfs1(int u, int p) {
  cc[u] = cur_cc;
  for (auto& v : g[u]) {
    if (v.first != p) {
      d[v.first] = d[u] + v.second;
      dfs1(v.first, u);
    }
  }
  mx[u] = d[u];
  vector<int> tmp = {0, 0};
  for (auto& v : g[u]) {
    mx[u] = max(mx[u], mx[v.first]);
    tmp.push_back(mx[v.first]);
  }
  sort(tmp.rbegin(), tmp.rend());
  diameter[cc[u]] = max(diameter[cc[u]], tmp[0] + tmp[1] - 2 * d[u]);
}

void dfs2(int u, int p, int len) {
  multiset<int> st;
  for (auto& v : g[u]) {
    if (v.first != p) {
      st.insert(mx[v.first]);
    }
  }
  for (auto& v : g[u]) {
    if (v.first != p) {
      st.erase(mx[v.first]);
      dfs2(v.first, u, max(len, (st.empty() ? 0 : *st.rbegin() - d[u])) + v.second);
      st.insert(mx[v.first]);
    }
  }
  mn[cc[u]] = min(mn[cc[u]], max(len, mx[u] - d[u]));
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
  g.resize(N);
  for (int i = 0; i < M; i++) g[A[i]].push_back({B[i], T[i]});
  for (int i = 0; i < M; i++) g[B[i]].push_back({A[i], T[i]});
  d.assign(N, 0);
  cc.assign(N, -1);
  mx.resize(N);
  for (int i = 0; i < N; i++) {
    if (cc[i] == -1) {
      diameter.push_back(0);
      dfs1(i, -1);
      cur_cc++;
    }
  }
  mn.assign(cur_cc, INF);
  for (int i = 0; i < N; i++) {
    if (mn[cc[i]] == INF) dfs2(i, -1, 0);
  }
  sort(mn.begin(), mn.end());
  int tmp = *max_element(diameter.begin(), diameter.end());
  if (cur_cc == 1) return tmp;
  if (cur_cc == 2) return max(tmp, mn[0] + mn[1] + L);
  return max({tmp, mn[cur_cc - 2] + mn[cur_cc - 3] + 2 * L, mn[cur_cc - 1] + mn[cur_cc - 2] + L});
}

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