Submission #135151

#	Time	Username	Problem	Language	Result	Execution time	Memory
135151		IOrtroiii	Highway Tolls (IOI18_highway)	C++14	100 / 100	353 ms	10988 KiB

highway

#include "highway.h"

#include <bits/stdc++.h>

using namespace std;

using ll = long long;

void find_pair(int n, vector<int> u, vector<int> v, int a, int b) {
   int m = u.size();
   vector<vector<pair<int, int>>> g(n);
   for (int i = 0; i < m; ++i) {
      g[u[i]].emplace_back(v[i], i);
      g[v[i]].emplace_back(u[i], i);
   }
   vector<int> w(m);
   ll dist = ask(w);
   int l = 0, r = m - 1;
   while (l < r) {
      int md = (l + r) >> 1;
      for (int i = 0; i < m; ++i) {
         w[i] = i <= md;
      }
      if (ask(w) != dist) {
         r = md;
      } else {
         l = md + 1;
      }
   }
   int id = l;
   vector<int> tr;
   vector<int> lc;
   vector<int> rc;
   vector<int> color(n);
   queue<int> q;
   color[u[id]] = 1;
   lc.push_back(u[id]);
   q.push(u[id]);
   color[v[id]] = 2;
   q.push(v[id]);
   rc.push_back(v[id]);
   tr.push_back(id);
   while (!q.empty()) {
      int u = q.front(); q.pop();
      for (auto e : g[u]) {
         int v, id;
         tie(v, id) = e;
         if (!color[v]) {
            if (color[u] == 1) {
               color[v] = 1;
               lc.push_back(v);
            } else {
               color[v] = 2;
               rc.push_back(v);
            }
            tr.push_back(id);
            q.push(v);
         }
      }
   }
   assert(tr.size() == n - 1);
   auto get = [&](vector<int> comp) {
      int sz = comp.size();
      int l = 0, r = sz - 1;
      while (l < r) {
         int md = (l + r) >> 1;
         vector<bool> was(n);
         for (int i = md + 1; i < sz; ++i) {
            was[comp[i]] = true;
         }
         for (int i = 0; i < m; ++i) {
            w[i] = was[u[i]] || was[v[i]];
         }
         if (ask(w) != dist) {
            l = md + 1;
         } else {
            r = md;
         }
      }
      return comp[l];
   };

   answer(get(lc), get(rc));
}

// g++ -std=c++14 grader.cpp highway.cpp

Compilation message (stderr)

In file included from /usr/include/c++/7/cassert:44:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:33,
                 from highway.cpp:3:
highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:61:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    assert(tr.size() == n - 1);
           ~~~~~~~~~~^~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 33 / 33
• Subtask 5: 18 / 18
• Subtask 6: 31 / 31