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  1. #include<bits/stdc++.h>
  2. #include<ext/pb_ds/assoc_container.hpp>
  3. #include<ext/pb_ds/tree_policy.hpp>
  4.  
  5. using namespace std;
  6. using namespace __gnu_pbds;
  7.  
  8.  
  9. #define int 					long long int
  10. #define f(i,x,n)			    for(int i=x;i<n;++i)
  11.  
  12. // ============================================================================================================
  13.  
  14. class Graph {
  15.  
  16. 	int V; //vertices
  17. 	list<pair<int, int>> *l; //adjacency list list of pointers to list
  18. 	// since it is a weighted graph hence we are storeing pair
  19. 	//x --> (y,cost)
  20.  
  21. public:
  22. 	Graph(int v) {
  23. 		V = v;
  24. 		l = new list<pair<int, int>>[V];
  25. 	}
  26.  
  27. 	void addEdge(int u, int v, int cost) {
  28. 		l[u].push_back({v, cost}); //Segmentation fault
  29. 		l[v].push_back({u, cost});
  30. 	}
  31.  
  32. 	int min(int a, int b) {
  33. 		if (a > b) return b;
  34. 		else return a;
  35. 	}
  36.  
  37. 	int dfsHelper(int n, bool *visited, int *count, int &ans) {
  38.  
  39. 		visited[n] = true;
  40. 		int res;
  41. 		for (auto i = l[n].begin(); i != l[n].end(); ++i) {
  42. 			if (!visited[n]) {
  43. 				res = dfsHelper((*i).first, visited, count, ans);
  44. 				ans += 2 * ((*i).second) * min(res, V - res);
  45. 				count[n] += res;
  46. 			}
  47. 		}
  48. 		return count[n];
  49. 	}
  50.  
  51. 	int dfs() {
  52. 		bool *visited = new bool[V];
  53. 		int *count = new int[V]; // count is for storing the count
  54. 		// of each node
  55.  
  56. 		for (int i = 0; i < V; ++i) {
  57. 			visited[i] = false;
  58. 			count[i] = 1;
  59. 		}
  60.  
  61. 		int ans = 0;
  62. 		dfsHelper(0, visited, count, ans);
  63. 		return ans;
  64. 	}
  65. };
  66.  
  67. int32_t main() {
  68.  
  69. 	int t;
  70. 	cin >> t;
  71. 	while (t--) {
  72. 		int n;
  73. 		cin >> n;
  74.  
  75. 		int x, y, z;
  76. 		Graph g(n);
  77. 		f(i, 0, n - 1) {
  78. 			cin >> x >> y >> z;
  79. 			g.addEdge(x, y, z);
  80. 		}
  81.  
  82. 		int ans = g.dfs();
  83.  
  84. 		cout << ans << endl;
  85. 	}
  86. 	return 0;
  87. }
  88.  
Success #stdin #stdout 0s 4176KB
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https://ideone.com/XxTpjf
language:
C++14 (gcc 8.3)
created:
3 years ago
visibility:
public

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