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  1.  
  2. #pragma GCC optimize("O3,unroll-loops")
  3. #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
  4.  
  5. #include <bits/stdc++.h>
  6. using namespace std;
  7.  
  8. #define files                         \
  9.     freopen("input.txt", "r", stdin); \
  10.     freopen("output.txt", "w", stdout);
  11.  
  12. #define rall(x) x.rbegin(), x.rend()
  13. #define all(x) x.begin(), x.end()
  14. #define sz(x) (int)x.size()
  15. #define ll long long
  16.  
  17. #define rep(ii, beg, till, inc) for (int ii = beg; ii < till; ii += inc)
  18. #define repr(ii, beg, till, inc) for (int ii = beg - 1; ii >= till; ii -= inc)
  19.  
  20. const ll MOD = 1e9 + 7;
  21. const int MXN = 2e5 + 5;
  22.  
  23. int dx[] = {1, -1, 0, 0};
  24. int dy[] = {0, 0, 1, -1};
  25.  
  26. int edges = 0;
  27. vector<int> graph[MXN];
  28. int dfs(int node, int par)
  29. {
  30.     int one = 0;
  31.     for (int child : graph[node])
  32.     {
  33.         if (child == par)
  34.             continue;
  35.         int cur = dfs(child, node);
  36.         edges += cur == 2;
  37.         one += cur == 1;
  38.     }
  39.     one = one != 0;
  40.     ++one;
  41.     edges += one == 2;
  42.     one %= 2;
  43.     return one;
  44. }
  45. void sol(int tc)
  46. {
  47.     int node;
  48.     cin >> node;
  49.     rep(ii, 1, node, 1)
  50.     {
  51.         int u, v;
  52.         cin >> u >> v;
  53.         graph[u].push_back(v);
  54.         swap(u, v);
  55.         graph[u].push_back(v);
  56.     }
  57.     dfs(1, 1);
  58.     cout << edges << "\n";
  59. }
  60.  
  61. int main()
  62. {
  63.     ios::sync_with_stdio(false);
  64.     cin.tie(nullptr);
  65.  
  66.     int T = 1;
  67.     // cin >> T;
  68.     for (int ii = 1; ii <= T; ++ii)
  69.         sol(ii);
  70. }
  71.  
Runtime error #stdin #stdout 0.01s 8012KB
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Standard input is empty
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Standard output is empty
https://ideone.com/gHz9Er
language:
C++ (gcc 8.3)
created:
209 days ago
visibility:
secret

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