Submission #1073808

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073808		shezitt	Highway Tolls (IOI18_highway)	C++14	12 / 100	77 ms	8528 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>

using ll = long long;
using namespace std;

#define pb push_back
#define sz(x) (int)x.size()

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
  int M = U.size();
  
  vector<int> tmp(M, 0);

  vector<vector<pair<int,int>>> adj(N+1);
  for(int i=0; i<M; ++i){
    adj[U[i]].pb({V[i], i});
    adj[V[i]].pb({U[i], i});
  }

  ll W = ask(tmp);
  int aristas = W / A;
  
  vector<int> pa(N+1, -1);

  auto bfs = [&](int at) -> vector<int> {
    vector<int> res;
    vector<int> dis(N+1, N+10);

    queue<int> q;
    q.push(at);
    dis[at] = 0;
    while(sz(q)){
      int cur = q.front();
      q.pop();
      if(dis[cur] == aristas){
        res.pb(cur);
      }
      for(auto [u, id] : adj[cur]){
        if(dis[cur] + 1 < dis[u]){
          dis[u] = dis[cur] + 1;
          q.push(u);
          pa[u] = id;
        }
      }
    }
    return res;
  };

  vector<int> cands = bfs(0);

  int ans = 0;
  int low = 0, high = sz(cands)-1;
  while(low <= high){
    int mid = (low + high) / 2;
    for(int i=0; i<=mid; ++i){
      tmp[pa[cands[i]]] = 1;
    }

    ll w = ask(tmp);
    if(w != W){
      ans = cands[mid];
      high = mid-1;
    } else {
      low = mid+1;
    }

    for(int i=0; i<=mid; ++i){
      tmp[pa[cands[i]]] = 0;
    }
  }
  
  answer(0, ans);

}

Compilation message (stderr)

highway.cpp: In lambda function:
highway.cpp:39:16: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   39 |       for(auto [u, id] : adj[cur]){
      |                ^

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 0 / 6
• Subtask 4: 0 / 33
• Subtask 5: 0 / 18
• Subtask 6: 0 / 31