Submission #703464

#	Time	Username	Problem	Language	Result	Execution time	Memory
703464		Darren0724	Star Trek (CEOI20_startrek)	C++17	15 / 100	1079 ms	484 KiB

startrek

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod=1e9+7;
int pw(int a,int b){
    int ans=1;
    while(b){
        if(b&1){
            ans=ans*a%mod;
        }
        b>>=1;
        a=a*a%mod;
    }
    return ans;
}
vector<vector<int>> adj;
vector<int> dp;
void dfs(int k,int pa){
    bool flag=0;
    for(int j:adj[k]){
        if(j==pa){
            continue;
        }
        dfs(j,k);
        if(dp[j]==0){
            flag=1;
        }
    }
    dp[k]=flag;
}
signed main(){
    int n;cin>>n;
    int d;cin>>d;
    if(n==2){
        int p=pw(2,d*2);
        cout<<p<<endl;
        return 0;
    }
    adj.resize(n*2);
    for(int i=1;i<n;i++){
        int a,b;cin>>a>>b;a--;b--;
        adj[a].push_back(b);
        adj[b].push_back(a);
        adj[n+a].push_back(n+b);
        adj[n+b].push_back(n+a);
    }
    int ans=0;
    for(int i=0;i<n;i++){
        for(int j=n;j<n*2;j++){
            adj[i].push_back(j);
            dp.assign(n*2,-1);
            dfs(0,0);
            if(dp[0]==1){
                ans++;
            }
            adj[i].pop_back();
        }
    }
    cout<<ans<<endl;

    return 0;
}

• Subtask 1: 0 / 0
• Subtask 2: 7 / 7
• Subtask 3: 8 / 8
• Subtask 4: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20
• Subtask 8: 0 / 15