Submission #867062

#	Time	Username	Problem	Language	Result	Execution time	Memory
867062		HossamHero7	The Xana coup (BOI21_xanadu)	C++14	15 / 100	70 ms	7516 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define endl '\n'
int n;
vector<bool> on;
int solve(int i,bool change,bool need){
    if(i == n) return (need ? 1e9 : 0);
    if(need) return solve(i+1,1,on[i]^change^1) + 1;
    return solve(i+1,0,on[i]^change);
}
void solve(){
    cin>>n;
    vector<vector<int>> adj(n);
    for(int i=0;i<n-1;i++){
        int a,b;
        cin>>a>>b;
        a -- , b --;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    if(n <= 20){
        int mask = 0;
        for(int i=0;i<n;i++){
            int x;
            cin>>x;
            if(!x) mask |= (1<<i);
        }
        queue<int> q;
        vector<int> dep((1<<n),-1);
        q.push(mask);
        dep[mask] = 0;
        while(q.size()){
            int mask = q.front();       q.pop();
            for(int i=0;i<n;i++){
                int nmask = mask ^ (1<<i);
                for(auto ch : adj[i]) nmask ^= (1<<ch);
                if(~dep[nmask]) continue;
                q.push(nmask);
                dep[nmask] = dep[mask] + 1;
            }
        }
        if(~dep[(1<<n)-1]) cout<<dep[(1<<n)-1]<<endl;
        else cout<<"impossible"<<endl;
    }
    else {
        on.resize(n);
        for(int i=0;i<n;i++){
            int x;cin>>x;
            if(x) on[i] = 1;
        }
        int ans = solve(0,0,0);
        if(ans >= 1e9) cout<<"impossible"<<endl;
        else cout<<ans<<endl;
    }
}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);      cout.tie(0);
    int t=1;
    //cin>>t;
    while(t--){
        solve();
    }
    return 0;
}

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