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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. const int N=1e5+10;
  4.  
  5. vector<int>g[N];
  6. int vis[N],color[N];
  7. int black=0;
  8. void dfs(int u,int co)
  9. {
  10. 	vis[u]=1;
  11. 	color[u]=co;
  12. 	for(auto i : g[u])
  13. 	{
  14. 		if(!vis[i])
  15. 			dfs(i,1-co);
  16. 	}
  17. }
  18. int main()
  19. {	
  20.  
  21.  	int n,mx;
  22.   	while(scanf("%d",&n)==1)
  23.   	{
  24.   		int u,v;
  25.   		for(int i=1;i<n;i++)
  26.   		{cin>>u>>v;
  27.   			g[u].push_back(v);
  28.  
  29. 			g[v].push_back(u);	
  30.   		}
  31.  
  32.   		dfs(1,1);
  33.  
  34.   		for(int i=1;i<=n;i++)
  35.   			if(color[i]==1)
  36.   				black++;
  37.   		long long ans=1LL*black*(n-black) - (n-1);
  38.   		printf("%lld\n",ans);
  39.   	}
  40.  
  41. }
Success #stdin #stdout 0s 18368KB
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https://ideone.com/Ur6hNP
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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