Submission #492045

#	Time	Username	Problem	Language	Result	Execution time	Memory
492045		lorenzoferrari	Dreaming (IOI13_dreaming)	C++14	0 / 100	1077 ms	12504 KiB

dreaming

// a) ans = max(diametri)
// b) max "code", dove coda = min(max distanza da un nodo)
//  if 1 componente: return ans
//  ans = max(ans, codaMax[0] + codaMax[1] + L)
//  if 2 componenti: return ans
//  ans = max(ans, codaMax[1] + codaMax[2] + 2*L)
//  return ans

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

vector<vector<int>> c;
vector<vector<pair<int, int>>> g;
vector<int> cmp;
int gty = 0;
array<int, 2> dmax;
vector<int> d, p, vis;

void dfs1(int v) {
  cmp[v] = gty;
  c.back().push_back(v);
  for (int i = 0; i < g[v].size(); ++i)
    if (cmp[g[v][i].first] != gty)
      dfs1(g[v][i].first);
}

void dfs(int v, int ty) {
  vis[v] = ty;
  if (d[v] > dmax[1])
    dmax = {v, d[v]};
  for (int i = 0; i < g[v].size(); ++i) {
    int u = g[v][i].first;
    int w = g[v][i].second;
    if (vis[u] != ty) {
      d[u] = d[v] + w;
      dfs(u, ty);
    }
  }
}

int diam(int v) {
  dmax = {v, 0}; dfs(v, gty++);
  v = dmax[0]; d[v] = 0;
  dfs(v, gty++);
  return dmax[1];
}

int coda(int v) {
  // cout << "coda[" << v << "] = ";
  // modo stupido O(n^2)
  int ans = 1e9;
  for (int u : c[cmp[v]]) {
    fill(d.begin(), d.end(), 0);
    dfs(u, gty++);
    ans = min(ans, *max_element(d.begin(), d.end()));
  }
  // cout << ans << "\n";
  return ans;
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
  g.resize(N);
  d.resize(N);
  p.resize(N, -1);
  vis.resize(N, -1);
  cmp.resize(N, -1);
  for (int i = 0; i < M; ++i) {
    g[A[i]].push_back({B[i], T[i]});
    g[B[i]].push_back({A[i], T[i]});
  }
  for (int i = 0; i < N; ++i) {
    if (cmp[i] == -1) {
      c.push_back(vector<int>(0));
      dfs1(i);
      ++gty;
    }
  }
  int kek = gty;
  int ans = 0;
  for (int i = 0; i < kek; ++i)
    ans = max(ans, diam(c[i][0]));
  array<int, 3> o{};
  for (int i = 0; i < kek; ++i) {
    o[2] = max(o[2], coda(c[i][0]));
    if (o[1] < o[2]) swap(o[1], o[2]);
    if (o[0] < o[1]) swap(o[0], o[1]);
  }
  // cout << o[0] << " " << o[1] << " " << o[2] << "\n";
  if (gty == 1) return ans;
  ans = max(ans, o[0] + o[1] + L);
  if (gty == 2) return ans;
  ans = max(ans, o[1] + o[2] + 2*L);
  return ans;
}

Compilation message (stderr)

dreaming.cpp: In function 'void dfs1(int)':
dreaming.cpp:23:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   23 |   for (int i = 0; i < g[v].size(); ++i)
      |                   ~~^~~~~~~~~~~~~
dreaming.cpp: In function 'void dfs(int, int)':
dreaming.cpp:32:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |   for (int i = 0; i < g[v].size(); ++i) {
      |                   ~~^~~~~~~~~~~~~

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