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  1. #include <bits/stdc++.h>
  2. #define TASK "TREEXOR"
  3. #define int long long
  4. #define MOD 1000000007
  5.  
  6. using namespace std;
  7.  
  8. int n, x;
  9. int a[100005], xo[100005], res = 0;
  10. vector <int> adj[100005];
  11.  
  12. void dfs(int u, int up) {
  13.     xo[u] = a[u];
  14.     for (int v : adj[u]) {
  15.         if (v != up) {
  16.             dfs(v, u);
  17.             xo[u] ^= xo[v];
  18.         }
  19.     }
  20.     if (xo[u] == x) {
  21.         res = (res == 0) ? 1 : res * 2 % MOD;
  22.     }
  23. }
  24.  
  25. signed main() {
  26.     if (fopen(TASK".inp", "r")) {
  27.         freopen(TASK".inp", "r", stdin);
  28.         freopen(TASK".out", "w", stdout);
  29.     }
  30.     ios_base::sync_with_stdio(0);
  31.     cin.tie(0);
  32.     cout.tie(0);
  33.     cin >> n >> x;
  34.     for (int i = 1; i <= n; i++) {
  35.         cin >> a[i];
  36.     }
  37.     for (int i = 1; i < n; i++) {
  38.         int u, v;
  39.         cin >> u >> v;
  40.         adj[u].push_back(v);
  41.         adj[v].push_back(u);
  42.     }
  43.     dfs(1, 0);
  44.     cout << res;
  45. }
  46.  
Success #stdin #stdout 0.01s 6452KB
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https://ideone.com/iLM3go
language:
C++ (gcc 8.3)
created:
22 hours ago
visibility:
public

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