Submission #934900

#	Time	Username	Problem	Language	Result	Execution time	Memory
934900		sleepntsheep	Highway Tolls (IOI18_highway)	C++17	6 / 100	121 ms	16512 KiB

highway

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

int n,m,a,b;std::vector<int>u,v;std::vector<std::pair<int,int>>g[90001];

int sub12(int src,int ban)
{
    vector<int>d(n,1e9),e(n,-1);
    queue<pair<int,int>>q; q.emplace(d[src]=0,src);
    while(q.size()){auto[c,u]=q.front();q.pop();for(auto[v,i]:g[u])if(ban-i&&d[v]>c+1)q.emplace(d[v]=c+1,v),e[v]=i;}

    long long need; {vector<int>qq(m);for(int i=0;i<n;++i)if(~e[i])qq[e[i]]=1;need=ask(qq);}

    vector<int>c;
    for(int i=0;i<n;++i)if(d[i]<1e9)c.push_back(i);
    sort(c.begin(),c.end(),[&d](int i,int v){return d[i]<d[v];});

    int z=0,l=0,r=c.size()-1;
    while(l<=r){
        int y=(l+r)/2;
        vector<int>qq(m,0);
        for(int i=1;i<=y;++i)if(~e[c[i]])qq[e[c[i]]]=1;
        if (ask(qq)==need)z=c[y],r=y-1;
        else l=y+1;
    }
    return z;
}

void sub1234(){
    long long need; {vector<int>qq(m,1); need=ask(qq);}
    auto dt = need / b;
    long long light = dt * a;

    int e1,l=0,r=m-1;
    while(l<=r) {
        int y=(l+r)/2;
        vector<int>qq(m);
        for(int i=0;i<=y;++i)qq[i]=1;
        if(ask(qq)>light)r=y-1,e1=y;
        else l=y+1;
    }

    int p=u[e1],q=v[e1],s=sub12(p,e1),t=sub12(q,e1);

    answer(s,t);
}

void sub5(){
    int l=0,r=n-1;

    auto diffset = [&](vector<int>&grp){
        vector<int>qq(m);
        for(int i=0;i<m;++i)if(grp[u[i]]^grp[v[i]])qq[i]=a;else qq[i]=b;
        if(ask(qq)&1)return 1;return 0;
    };

    vector<int> gs,gt,grp(n);

    for(int b=0;b<=17;++b){
        for(int i=0;i<n;++i)
            grp[i]=(i>>b)&1;
        if(diffset(grp)) {break;}
    }

    for(int i=0;i<n;++i)if(grp[i])gt.push_back(i);else gs.push_back(i);

    while(gs.size()>1){
        vector<int>n1,n2;
        for(int i=0;i<gs.size()/2;++i)n1.push_back(gs[i]);
        for(int i=gs.size()/2;i<gs.size();++i)n2.push_back(gs[i]);
        vector<int> test(n);for(int x:n1)test[x]=1;
        if(diffset(test))gs=n1;
        else gs=n2;
    }

    while(gt.size()>1){
        vector<int>n1,n2;
        for(int i=0;i<gt.size()/2;++i)n1.push_back(gt[i]);
        for(int i=gt.size()/2;i<gt.size();++i)n2.push_back(gt[i]);
        vector<int> test(n);for(int x:n1)test[x]=1;
        if(diffset(test))gt=n1;
        else gt=n2;
    }
    answer(gs[0],gt[0]);
}

void find_pair(int n_, std::vector<int> u_, std::vector<int> v_, int A_, int B_) {
    n=n_,u=u_,v=v_,a=A_,b=B_;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});

    if(a==1&&b==2)return sub5();
    sub1234();

}

Compilation message (stderr)

highway.cpp: In lambda function:
highway.cpp:55:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   55 |         if(ask(qq)&1)return 1;return 0;
      |         ^~
highway.cpp:55:31: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
   55 |         if(ask(qq)&1)return 1;return 0;
      |                               ^~~~~~
highway.cpp: In function 'void sub5()':
highway.cpp:70:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |         for(int i=0;i<gs.size()/2;++i)n1.push_back(gs[i]);
      |                     ~^~~~~~~~~~~~
highway.cpp:71:32: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |         for(int i=gs.size()/2;i<gs.size();++i)n2.push_back(gs[i]);
      |                               ~^~~~~~~~~~
highway.cpp:79:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   79 |         for(int i=0;i<gt.size()/2;++i)n1.push_back(gt[i]);
      |                     ~^~~~~~~~~~~~
highway.cpp:80:32: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   80 |         for(int i=gt.size()/2;i<gt.size();++i)n2.push_back(gt[i]);
      |                               ~^~~~~~~~~~
highway.cpp:50:9: warning: unused variable 'l' [-Wunused-variable]
   50 |     int l=0,r=n-1;
      |         ^
highway.cpp:50:13: warning: unused variable 'r' [-Wunused-variable]
   50 |     int l=0,r=n-1;
      |             ^
highway.cpp: In function 'void sub1234()':
highway.cpp:44:15: warning: 'e1' may be used uninitialized in this function [-Wmaybe-uninitialized]
   44 |     int p=u[e1],q=v[e1],s=sub12(p,e1),t=sub12(q,e1);
      |               ^

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