Submission #783600

#	Time	Username	Problem	Language	Result	Execution time	Memory
783600		christinelynn	The Xana coup (BOI21_xanadu)	C++17	5 / 100	1081 ms	7272 KiB

xanadu

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int MAX=1e9;
int n;
vector<vector<int>> adj;
bool can(vector<int> c, int mask) {
  int i=0;
  while(mask) {
    if(mask&1) {
      c[i]^=1;
      for(int p : adj[i]) c[p]^=1;
    }
    mask>>=1; i++;
  }
  int sum=0;
  for(int p : c) sum+=p;
  return sum==0;
}
signed main() {
  ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  cin >> n; adj.resize(n);
  for(int i=1; i<n; i++) {
    int u, v; cin >> u >> v; --u; --v;
    adj[u].push_back(v);
    adj[v].push_back(u);
  }
  int ans=MAX;
  vector<int> c(n); for(int &p : c) cin >> p;
  for(int i=0; i<(1 << n); i++) 
    if(can(c, i)) ans=min(ans, (int)__builtin_popcount(i)); 
  if(ans>=MAX) cout << "impossible\n";
  else cout << ans << '\n';
    return 0;
}

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