fork(2) download
copy 
  1. #include <iostream>
  2. #include <vector>
  3. using namespace std;
  4. vector<long long> adj[100001];
  5. double down[100001];
  6. double up[100001];
  7. long long childcnt[100001];
  8. long long n,x,y;
  9. vector<long long> tim;
  10. double dfs(long long pos, long long par){
  11. 	long long cnt=0;
  12. 	double tot = 0;
  13. 	for(long long i : adj[pos]){
  14. 		if(i==par)	continue;
  15. 		cnt++;
  16. 		tot+=dfs(i,pos);
  17. 	}
  18. 	double val = 0;
  19. 	if(cnt>0)	tot/=cnt;
  20. 	down[pos]=val+tot;
  21. 	childcnt[pos]=cnt;
  22. 	return down[pos]+tim[pos];
  23. }
  24.  
  25. void dfs1(long long pos, long long par){
  26. 	up[pos]=tim[par];
  27. 	double val = down[par];
  28. 	val*=childcnt[par];
  29. 	val-=tim[pos];
  30. 	val-=down[pos];
  31. 	val+=up[par];
  32. 	if(par==1){
  33. 		if(childcnt[par]>1)
  34. 			val/=(childcnt[par]-1);
  35. 	}
  36. 	else{
  37. 		if(childcnt[par]>0)
  38. 			val/=(childcnt[par]);
  39. 	}
  40. 	up[pos]+=val;
  41. 	for(long long i : adj[pos]){
  42. 		if(i==par)	continue;
  43. 		dfs1(i,pos);
  44. 	}
  45. }
  46. int main() {
  47. 	cin>>n;
  48. 	tim.resize(n+1);
  49. 	for(long long i = 1 ; i<=n ; i++)	cin>>tim[i];
  50. 	for(long long i = 1; i<n ; i++){
  51. 		cin>>x>>y;
  52. 		adj[x].push_back(y);
  53. 		adj[y].push_back(x);
  54. 	}
  55. 	dfs(1,1);
  56. 	up[1]=0;
  57. 	for(long long i : adj[1])
  58. 		dfs1(i,1);
  59. 	double minval = 1e200;
  60. 	double minpos = -1;
  61. 	for(long long i = 1; i<=n; i++){
  62. 		double val = 0.0;
  63. 		if(childcnt[i]==0) val = up[i]+tim[i];
  64. 		else if(i==1)	val=down[i]+tim[i];
  65. 		else{
  66. 			val = down[i]*childcnt[i];
  67. 			val+=up[i];
  68. 			val/=(childcnt[i]+1);
  69. 			val+=tim[i];
  70. 		}
  71. 		if(val<minval){
  72. 			minval = val;
  73. 			minpos = i;
  74. 		}
  75. 	}
  76. 	cout<<minpos;
  77. 	return 0;
  78. }
Success #stdin #stdout 0s 6980KB
comments (?)
stdin
copy 
7
2 3 3 5 1 2 1
1 2
4 5
5 3
3 1
1 7
2 6
stdout
copy 
1
https://ideone.com/YMV8oV
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!