Dijkstraクラスの作成

lib/Graph/dijkstra.h

@@ -0,0 +1,69 @@
+#pragma once
+#include "graph.h"
+#include "template.h"
+
+template <typename T>
+class Dijkstra {
+ private:
+  T INF = numeric_limits<T>::max() / 10;
+  int V;           // 頂点数
+  AdjList<T> adj;  // adj[始点][動的配列で始点から伸びる枝]
+  vector<int> prever;
+
+ public:
+  explicit Dijkstra(int n);
+  vector<T> cost;
+  void AddEdge(int f, int t, int c);
+  bool HasPath(int t);                 // tに至るパスはあるか
+  vector<int> GetShortestPath(int t);  // tへの最短路
+  void Run(int f);
+};
+
+template <typename T>
+Dijkstra<T>::Dijkstra(int n)
+    : V(n + 1), adj(V), prever(vector<int>(V, -1)), cost(V) {
+  fill(cost.begin(), cost.end(), INF);
+}
+
+template <typename T>
+void Dijkstra<T>::AddEdge(int f, int t, int c) {
+  adj[f].push_back(Edge<T>(t, c));
+}
+
+template <typename T>
+bool Dijkstra<T>::HasPath(int t) {
+  return cost[t] != INF;
+}
+
+template <typename T>
+vector<int> Dijkstra<T>::GetShortestPath(int t) {
+  vector<int> path;
+  for (; t != -1; t = prever[t]) path.push_back(t);
+
+  reverse(path.begin(), path.end());
+  return path;
+}
+
+template <typename T>
+void Dijkstra<T>::Run(int firstNode) {
+  using Pi = pair<T, int>;
+  priority_queue<Pi, vector<Pi>, greater<Pi>> pq;
+
+  cost[firstNode] = 0;
+  pq.push(Pi(cost[firstNode], firstNode));
+
+  while (!pq.empty()) {
+    Pi currentEdge = pq.top();
+    pq.pop();
+    if (cost[currentEdge.second] < currentEdge.first) continue;
+
+    for (Edge<T> tmp : adj[currentEdge.second]) {
+      T sumCost = currentEdge.first + tmp.cost;
+      if (cost[tmp.to] > sumCost) {
+        cost[tmp.to] = sumCost;
+        prever[tmp.to] = currentEdge.second;
+        pq.push(Pi(cost[tmp.to], tmp.to));
+      }
+    }
+  }
+}