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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3.  
  4. const long long MaxN = 1e5 + 5;
  5.  
  6. long long n,sz[MaxN];
  7. vector<long long> a[MaxN];
  8.  
  9. void input()
  10. {
  11.     cin >> n;
  12.  
  13.     for(long long i=1;i<=n-1;i++)
  14.     {
  15.         long long u,v;
  16.         cin >> u >> v;
  17.         a[u].push_back(v);
  18.         a[v].push_back(u);
  19.     }
  20. }
  21.  
  22. void dfs(long long i,long long par,vector<long long> a[],long long sz[])
  23. {
  24.     for(long long x:a[i])
  25.     {
  26.         if(x!=par)
  27.         {
  28.             dfs(x,i,a,sz);
  29.             sz[i]+=sz[x];
  30.         }
  31.     }
  32. }
  33.  
  34. void solve()
  35. {
  36.     for(long long i=1;i<=n;i++)
  37.     {
  38.         sz[i]=1;
  39.     }
  40.  
  41.     dfs(1,1,a,sz);
  42.  
  43.     long long res=0;
  44.  
  45.     for(long long i=2;i<=n;i++)
  46.     {
  47.         res+=sz[i]*(n-sz[i]);
  48.     }
  49.  
  50.     cout << res;
  51. }
  52.  
  53. int main()
  54. {
  55.     ios_base::sync_with_stdio(0);
  56.     cin.tie(0);
  57.  
  58.     input();
  59.     solve();
  60. }
Success #stdin #stdout 0.01s 6396KB
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Standard output is empty
https://ideone.com/EB9DYl
language:
C++14 (gcc 8.3)
created:
3 days ago
visibility:
public

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