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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. const long long MaxN = 1e5 + 5, MOD= 1e9+7;
  4. long long n, dp[MaxN];
  5. vector<long long> a[MaxN];
  6. void dfs(long long u, long long par)
  7. {
  8.     for (long long v : a[u])
  9.     {
  10.         if(v==par) continue;
  11.         dfs(v,u);
  12.         dp[u]=((dp[u]%MOD)*(dp[v]+1)%MOD)%MOD;
  13.  
  14.     }
  15. }
  16. void input()
  17. {
  18.     cin >> n;
  19.     for (long long i=1; i<n ;i++)
  20.     {
  21.         long long u,v;
  22.         cin >> u >> v;
  23.         a[u].push_back(v);
  24.         a[v].push_back(u);
  25.     }
  26. }
  27. void solve()
  28. {
  29.     memset(dp,0,sizeof(dp));
  30.     for (long long i=1; i<=n ;i++)
  31.     {
  32.         dp[i]=1;
  33.     }
  34.     dfs(1,-1);
  35.     long long ans=0;
  36.     for (long long i=1; i<=n; i++)
  37.     {
  38.         ans=(ans+ dp[i])%MOD;
  39.     }
  40.     cout << ans;
  41. }
  42. int main()
  43. {
  44.     ios_base::sync_with_stdio(0);
  45.     cin.tie(0);
  46.     input();
  47.     solve();
  48. }
Success #stdin #stdout 0.01s 6816KB
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https://ideone.com/3nzwHx
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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