Submission #782867

#	Time	Username	Problem	Language	Result	Execution time	Memory
782867		devariaota	The Xana coup (BOI21_xanadu)	C++17	0 / 100	38 ms	11204 KiB

xanadu

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
#define endl "\n"
#define pii pair<ll,ll>
#define pb push_back
#define vi vector<ll>
#define pque priority_queue
#define pqueg priority_queue<ll,vector<ll>,greater<ll>>
#define que queue<ll>
#define FOR(m,i,n) for(int i=(m); i<=(n); i++)
#define FORM(m,i,n) for(int i=(m); i>=(n); i--)
ll n,u,v,ans;
vector<ll> adj[100100];
bool vis[100100];
ll a[100100];
void dfs(ll x) {
  vis[x] = true;
  for(auto i : adj[x]) {
    if(!vis[i]) {
      if(a[i] == 1 && i != n-1) {
        a[i] = 0;
        a[i+1] = a[i+1] ^ 1 ^ 0;
        a[i+2] = a[i+2] ^ 1 ^ 0;
        ans++;
      }
      dfs(i);
    }
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> n;
  FOR(1,i,n-1) {
    cin >> u >> v;
    adj[u].pb(v);
    adj[v].pb(u);
  }
  FOR(1,i,n) {
    cin >> a[i];
  }
  adj[0].pb(1);
  adj[1].pb(0);
  dfs(0);
  FOR(1,i,n) {
    if(a[i] == 1) {
      cout << "impossible" << endl;
      return 0;
    }
  }
  cout << ans << endl;
}

/*
5
1 2
2 3
3 4
4 5
1 0 1 0 1
*/

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