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  1. #include <iostream>
  2. #include <vector>
  3. #include <algorithm>
  4.  
  5. using namespace std;
  6.  
  7. long long dist[1001][1001];
  8. long long cost[1001][1001];
  9.  
  10. vector<int> g[1001];
  11.  
  12. void dfs(int v, int p, int f, long long c)
  13. {
  14.     dist[f][v] = dist[v][f] = c;
  15.  
  16.     for (int adj_v : g[v])
  17.         if (adj_v != p)
  18.             dfs(adj_v, v, f, c + cost[v][adj_v]);
  19. }
  20.  
  21. void print_best_path(int next[1000])
  22. {
  23. 	int v0 = 1;
  24. 	int v1 = next[v0];
  25. 	do
  26. 	{
  27. 		cout << v0 << " -> ";
  28.  
  29.         v0 = v1;
  30.         v1 = next[v0];
  31.  
  32.     } while (v0 != 1);
  33.  
  34. 	cout << "1\n";
  35. }
  36.  
  37. int main()
  38. {
  39.     int T;
  40.     cin >> T;
  41.  
  42.     for (int test_case = 1; test_case <= T; test_case++)
  43.     {
  44.         int n, k;
  45.         cin >> n >> k;
  46.  
  47.         for (int v = 1; v <= n; v++)
  48.             g[v].clear();
  49.  
  50.         for (int v = 2; v <= n; v++)
  51.         {
  52.             int parent, length;
  53.             cin >> parent >> length;
  54.  
  55.             cost[parent][v] = cost[v][parent] = length;
  56.             g[v].push_back(parent);
  57.             g[parent].push_back(v);
  58.         }
  59.  
  60.         for (int v = 1; v <= n; v++)
  61.             dfs(v, v, v, 0);
  62.  
  63.         int max_v = 2;
  64.         for (int v = 3; v <= n; v++)
  65.             if (dist[1][v] > dist[1][max_v])
  66.                 max_v = v;
  67.  
  68.         bool used[1001] = {};
  69.         int next[1001] = {};
  70.  
  71.         next[1] = max_v;
  72.         next[max_v] = 1;
  73.         used[max_v] = true;
  74.  
  75.         long long max_path_length = 2 * dist[1][max_v];
  76.  
  77.         cout << "max_v=" << max_v << endl;
  78.  		cout << "max_path_length=" << max_path_length << endl;
  79.  		print_best_path(next);
  80.  
  81.         for (int i = 2; i <= k; i++)
  82.         {
  83.             int best_v = -1;
  84.             int best_place = -1;
  85.             long long best_increase = -1;
  86.  
  87.             for (int v = 2; v <= n; v++)
  88.                 if (!used[v])
  89.                 {
  90.                     int v0 = 1;
  91.                     int v1 = next[v0];
  92.                     do
  93.                     {
  94.                         long long cur_dist = dist[v0][v1];
  95.                         long long new_dist = dist[v0][v] + dist[v][v1];
  96.                         long long increase = new_dist - cur_dist;
  97.  
  98.                         if (increase > best_increase)
  99.                         {
  100.                             best_increase = increase;
  101.                             best_v = v;
  102.                             best_place = v0;
  103.                         }
  104.  
  105.                         v0 = v1;
  106.                         v1 = next[v0];
  107.  
  108.                     } while (v0 != 1);
  109.                 }
  110.  
  111.             used[best_v] = true;
  112.  
  113.             int tmp = next[best_place];
  114.             next[best_place] = best_v;
  115.             next[best_v] = tmp;
  116.  
  117.             max_path_length += best_increase;
  118.  
  119.             cout << "best_v=" << best_v << " best_increase=" << best_increase <<
  120.             " max_path_length=" << max_path_length << endl;
  121.             print_best_path(next);
  122.         }
  123.  
  124.         cout << "Case #" << test_case << ": " << max_path_length;
  125.         if (test_case < T)
  126.             cout << '\n';
  127.     }
  128. }
Success #stdin #stdout 0s 30920KB
comments (?)
stdin
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1
5 3
1 10
2 20
2 20
1 20
stdout
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max_v=3
max_path_length=60
1 -> 3 -> 1
best_v=4 best_increase=40 max_path_length=100
1 -> 4 -> 3 -> 1
best_v=5 best_increase=60 max_path_length=160
1 -> 4 -> 5 -> 3 -> 1
Case #1: 160
https://ideone.com/uQebyB
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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