Submission #876599

#	Time	Username	Problem	Language	Result	Execution time	Memory
876599		davinpwk	The Xana coup (BOI21_xanadu)	C++14	100 / 100	42 ms	15720 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define fi first
#define se second
#define pb push_back
#define TC int t; cin>>t; while(t--)
#define all(x) (x).begin(),(x).end()
//*AC BERSAMA ALLAH  FORTIS FORTUNA ADIUVAT
const ll nx = 1e5+5;
vector<ll> adj[nx];
bool on[nx], vis[nx];
ll dp[nx][2][2];
ll n;

void dfs(ll nd){
    vis[nd] = 1;
    if(on[nd])
        dp[nd][1][0] = 1, dp[nd][0][1] = 0;
    else
        dp[nd][1][1] = 1, dp[nd][0][0] = 0;
    for(ll i : adj[nd]){
        if(!vis[i]){
            dfs(i);
            ll x = dp[nd][0][0], y = dp[nd][0][1];
            dp[nd][0][0] = min(x + dp[i][0][0], y + dp[i][1][0]);
            dp[nd][0][1] = min(y + dp[i][0][0], x + dp[i][1][0]);
            x = dp[nd][1][0], y = dp[nd][1][1];
            dp[nd][1][0] = min(x + dp[i][0][1], y + dp[i][1][1]);
            dp[nd][1][1] = min(y + dp[i][0][1], x + dp[i][1][1]);
        }
    }
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    cin >> n;
    for(ll i=1; i<n; i++){
        ll u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    for(ll i=1; i<=n; i++){
        cin >> on[i];
    }
    for(ll i=1; i<=n; i++){
        for(ll j=0; j<=1; j++)
            dp[i][j][0] = dp[i][j][1] = 1e6;
    }

    dfs(1);
    if(min(dp[1][1][0], dp[1][0][0]) > n){
        cout << "impossible\n";
    }
    else cout << min(dp[1][1][0], dp[1][0][0]) << '\n';

    return 0;
}

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