Submission #578708

#	Time	Username	Problem	Language	Result	Execution time	Memory
578708		ogibogi2004	Highway Tolls (IOI18_highway)	C++14	51 / 100	255 ms	262144 KiB

highway

#include "highway.h"
#include<bits/stdc++.h>
using namespace std;
const int MAXN=9e4+6;
vector<pair<int,int> >g[MAXN];
int par[MAXN];
int parEdge[MAXN];
vector<int>order;
void dfs(int u,int p)
{
    order.push_back(u);
    for(auto xd:g[u])
    {
        if(xd.first==p)continue;
        par[xd.first]=u;
        parEdge[xd.first]=xd.second;
        dfs(xd.first,u);
        order.push_back(u);
    }
}
void find_pair(int N, vector<int> U, vector<int> V, int A, int B) {
    int M = U.size();
    for(int i=0;i<M;i++)
    {
        g[U[i]].push_back({V[i],i});
        g[V[i]].push_back({U[i],i});
    }
    parEdge[0]=-1;
    par[0]=-1;
    dfs(0,-1);
    int low=0,high=order.size()-1,s,t;
    long long dist;
    vector<int>w;
    for(int i=0;i<M;i++)w.push_back(0);
    dist=(long long)ask(w)/A;
    while(low<=high)
    {
        int mid=(low+high)/2;
        for(int j=0;j<w.size();j++)w[j]=0;
        for(int j=0;j<mid;j++)
        {
            int x=order[j],y=order[j+1];
            if(par[x]==y)w[parEdge[x]]=1;
            else w[parEdge[y]]=1;
        }
        int cntheavy=(long long)(ask(w)-dist*A)/(B-A);
        if(cntheavy==dist)
        {
            s=mid;
            high=mid-1;
        }
        else low=mid+1;
    }
    low=0;high=order.size()-1;
    while(low<=high)
    {
        int mid=(low+high)/2;
        for(int j=0;j<w.size();j++)w[j]=0;
        for(int j=mid;j<s;j++)
        {
            int x=order[j],y=order[j+1];
            if(par[x]==y)w[parEdge[x]]=1;
            else w[parEdge[y]]=1;
        }
        int cntheavy=(long long)(ask(w)-dist*A)/(B-A);
        if(cntheavy==dist)
        {
            t=mid;
            low=mid+1;
        }
        else high=mid-1;
    }
    /*for(auto xd:order)cout<<xd<<" ";
    cout<<endl;
    cout<<s<<" "<<t<<endl;
    cout<<order[s]<<" "<<order[t]<<endl;*/
    answer(order[s],order[t]);
}

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:39:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |         for(int j=0;j<w.size();j++)w[j]=0;
      |                     ~^~~~~~~~~
highway.cpp:58:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |         for(int j=0;j<w.size();j++)w[j]=0;
      |                     ~^~~~~~~~~
highway.cpp:77:28: warning: 't' may be used uninitialized in this function [-Wmaybe-uninitialized]
   77 |     answer(order[s],order[t]);
      |                            ^
highway.cpp:31:35: warning: 's' may be used uninitialized in this function [-Wmaybe-uninitialized]
   31 |     int low=0,high=order.size()-1,s,t;
      |                                   ^

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