Submission #1056760

#	Time	Username	Problem	Language	Result	Execution time	Memory
1056760		user736482	The Xana coup (BOI21_xanadu)	C++17	5 / 100	449 ms	8564 KiB

xanadu

#include<bits/stdc++.h>
using namespace std;
long long a,b,c,t,n;
long long ans=1e9;
set<pair<long long,long long>>s;
vector<long long>tree[100007];
vector<long long>leaves;
vector<bool>st;
long long buttons[100007];
long long cost[100007][2][2];//vertice, iflit,ifpressed
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin>>n;
    for(long long i=1;i<n;i++){
        cin>>a>>b;
        tree[a].push_back(b);
        tree[b].push_back(a);
        buttons[a]+=1<<(b-1);
        buttons[b]+=1<<(a-1);
    }
    for(long long i=1;i<=n;i++){
        if(tree[i].size()==1)
            leaves.push_back(i);
        buttons[i]+=1<<(i-1);
        cin>>a;
        st.push_back(a);
    }
    reverse(st.begin(),st.end());
    long long a=0;
    for(long long i=0;i<st.size();i++){
        a*=2;
        a+=st[i];
    }
    for(long long i=0;i<1<<(n/2);i++){
        long long bits=0;
        long long res=0;
        for(long long j=0;j<n/2;j++){
            if(i&(1<<j)){
                bits++;
                res^=buttons[j+1];
            }
        }
        s.insert({res,bits});
        //cout<<res<<" "<<bits<<"\n";
    }
    for(long long i=0;i<(1LL<<((n+1)/2));i++){
        long long bits=0;
        long long res=a;
        for(long long j=0;j<(n+1)/2;j++){
            if(i&(1LL<<j)){
                bits++;
                res^=buttons[j+n/2+1];
            }
        }
        if(s.lower_bound({res,-1})==s.end()) continue;
        pair<long long,long long>ak=*s.lower_bound({res,-1});
        //cout<<ak.first<<" "<<ak.second<<" "<<res<<" "<<bits<<"\n";
        if(ak.first==res)
            ans=min(ans,bits+ak.second);
    }
    if(ans==1e9)
        cout<<"impossible";
    else
        cout<<ans;
    return 0;
}

Compilation message (stderr)

xanadu.cpp: In function 'int main()':
xanadu.cpp:31:24: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<bool>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |     for(long long i=0;i<st.size();i++){
      |                       ~^~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 0 / 15
• Subtask 3: 0 / 10
• Subtask 4: 0 / 40
• Subtask 5: 0 / 30