Submission #1095873

#	Time	Username	Problem	Language	Result	Execution time	Memory
1095873		owoovo	Highway Tolls (IOI18_highway)	C++17	12 / 100	249 ms	262144 KiB

highway

#include "highway.h"
#include<bits/stdc++.h>
#define ll long long
#define F first 
#define S second 
using namespace std;
vector<pair<int,int>> e[90010];
vector<int> w;
int n,dp[90010],toe[90010];
void dfs(int now,int last){
  dp[now]=dp[last]+1;
  for(auto x:e[now]){
    if(x.F==last)continue;
    toe[x.F]=x.S;
    dfs(x.F,now);
  }
  return;
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
  int M = U.size();
  w.resize(M);
  for(auto x:w)x=0;
  for(int i=0;i<M;i++){
    e[U[i]].push_back({V[i],i});
    e[V[i]].push_back({U[i],i});
  }
  dp[0]=-1;
  dfs(0,0);
  ll now=ask(w);
  ll need=now/A;
  vector<int> may;
  for(int i=0;i<N;i++){
    if(dp[i]==need)may.push_back(i);
  }
  int l=0,r=may.size();
  while(l<r-1){
    int m=(l+r)>>1;
    //cout<<l<<" "<<r<<" "<<m<<"\n";
    for(int i=0;i<M;i++)w[i]=0;
    for(int i=l;i<m;i++){
      w[toe[may[i]]]=1;
    }
    ll ne=ask(w);
    if(ne!=now){
      r=m;
    }else{
      l=m;
    }
  }
  //cout<<may[l]<<"\n";
  answer(0, may[l]);
  return;
}

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:22:12: warning: variable 'x' set but not used [-Wunused-but-set-variable]
   22 |   for(auto x:w)x=0;
      |            ^

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