Submission #942780

#	Time	Username	Problem	Language	Result	Execution time	Memory
942780		Darren0724	The Xana coup (BOI21_xanadu)	C++17	100 / 100	68 ms	33896 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;
#define LCBorz ios_base::sync_with_stdio(false); cin.tie(0);
#define int long long
#define all(x) x.begin(), x.end()
#define endl '\n'
const int N=200005;
const int INF=1e9;
vector<int> adj[N];
vector dp(4,vector<int>(N,INF));
vector v(N,0);
void dfs(int k,int pa){
    vector<int> dp0,dp1;
    int t0=0,t1=0;
    for(int j:adj[k]){
        if(j==pa)continue;
        dfs(j,k);
        t0+=dp[0][j];
        dp0.push_back({dp[1][j]-dp[0][j]});
        t1+=dp[2][j];
        dp1.push_back({dp[3][j]-dp[2][j]});
    }
    sort(all(dp0));
    sort(all(dp1));
    int now=v[k]*2;
    dp[now][k]=min(dp[now][k],t0);
    for(int j:dp0){
        now^=2;
        t0+=j;
        dp[now][k]=min(dp[now][k],t0);
    }
    now=(v[k]^1)*2+1;
    dp[now][k]=min(dp[now][k],t1+1);
    for(int j:dp1){
        now^=2;
        t1+=j;
        dp[now][k]=min(dp[now][k],t1+1);
    }
}
// change to 0 
int32_t main() {
    LCBorz;
    int n;cin>>n;
    for(int i=1;i<n;i++){
        int a,b;cin>>a>>b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    for(int i=1;i<=n;i++){
        cin>>v[i];
    }
    dfs(1,1);
    int ans=min(dp[0][1],dp[1][1]);
    if(ans==INF){
        cout<<"impossible"<<endl;
    }
    else{
        cout<<ans<<endl;
    }
    return 0;
}

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