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  1. #include <climits>
  2. #include <vector>
  3. #include <iostream>
  4. #include <algorithm>
  5. #include <queue>
  6.  
  7. void print( std::vector<int> & a )
  8. {
  9.     for (auto i : a)
  10.         std::cout << i << " ";
  11.     std::cout << std::endl;
  12. }
  13.  
  14. class Graph
  15. {
  16. private:
  17.     std::vector<std::vector<std::pair<int, int>>> adj;
  18.     std::vector<int> distances;
  19.     std::vector<int> path;
  20.     const int INF = INT_MAX;
  21.     int vertexes_count = 0, edges_count = 0;
  22.     void relax (int start, int end, int length);
  23. public:
  24.     typedef std::vector<int> result;
  25.     Graph();
  26.     Graph(int vertexes, int edges);
  27.     ~Graph();
  28.     void input();
  29.     void output();
  30.     result dijkstra(int start);
  31. };
  32.  
  33. Graph::Graph() {}
  34.  
  35. Graph::~Graph() {}
  36.  
  37. Graph::Graph(int vertexes, int edges)
  38. {
  39.     vertexes_count = vertexes;
  40.     edges_count    = edges;
  41.     adj.resize(vertexes + 1);
  42.     distances.resize(vertexes + 1, INF);
  43.     path.resize(vertexes + 1, -1);
  44. }
  45.  
  46. void Graph::input()
  47. {
  48.     int start = 0, end = 0, length = 0;
  49.     for (int i = 0; i < edges_count; ++i)
  50.     {
  51.         std::cin >> start >> end >> length;
  52.         adj[start].push_back (std::make_pair(length, end));
  53.         adj[end].push_back (std::make_pair(length, start));
  54.     }
  55. }
  56.  
  57. Graph::result
  58. Graph::dijkstra (int start)
  59. {
  60.     distances[start] = 0;
  61.     path[start] = start;
  62.     std::priority_queue<std::pair<int, int>,
  63.                         std::vector<std::pair<int, int>>,
  64.                         std::greater<std::pair<int, int>>> q;
  65.     q.push(std::make_pair(0, start));
  66.     while (!q.empty())
  67.     {
  68.         int current = q.top().second;
  69.         int len     = q.top().first;
  70.         q.pop();
  71.         for (int i = 0; i < adj[current].size(); ++i)
  72.         {
  73.             int to     = adj[current][i].second;
  74.             int length = adj[current][i].first;
  75.             // Relaxations
  76.             if (distances[to] > distances[current] + length)
  77.             {
  78.                 path[to] = current;     
  79.                 distances[to] = distances[current] + length;
  80.                 q.push(std::make_pair(distances[to], to));
  81.             }
  82.         }
  83.     }
  84.     // Replace INF by -1
  85.     //std::replace (distances.begin(), distances.end(), INF, -1);
  86.     print(distances);
  87.     return distances;
  88. }
  89.  
  90.  
  91. int main() {
  92.     int ntests = 0, nodes = 0, edges = 0, start = 0;
  93.     std::cin >> ntests;
  94.     for (int i = 0; i < ntests; ++i)
  95.     {
  96.         std::cin >> nodes >> edges;
  97.         Graph g(nodes, edges);
  98.         g.input();
  99.         std::cin >> start;
  100.         auto result = g.dijkstra (start);
  101.         print(result);
  102.     }
  103.     return 0;
  104. }
Success #stdin #stdout 0s 3468KB
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https://ideone.com/Ye8wWU
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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