Updated dijkstra

Author: FreeTymeKiyan

Other/Dijkstra.java

@@ -0,0 +1,83 @@
+import java.util.*;
+
+/**
+ * Dijkstra's Algorithm
+ * Find the shortest weighted path from some starting vertex to all vertices.
+ * Edges have non-negative weight
+ * 
+ * Tags: Graph
+ */
+class Dijkstra {
+    
+    public static void main(String[] args) {
+        
+    }
+
+    /**
+     * Create a wrapper class for edge
+     */
+    class Path implements Comparable<Path> {
+        Vertex dest;
+        double cost;
+        
+        public Path(Vertex d, double c) {
+            dest = d;
+            cost = c;
+        }
+        
+        @Override
+        public int compareTo(Path rhs) {
+            double otherCost = rhs.cost;
+            return cost < otherCost ? -1 : cost > otherCost ? 1 : 0;
+        }
+    }
+    
+    HashMap<String, Vertex> vertexMap = new HashMap<String, Vertex>();
+    
+    public void dijkstra(String startName) {
+        PriorityQueue<Path> pq = new PriorityQueue<Path>();
+        Vertex start = vertexMap.get(startName);
+        if (start == null) 
+            throw new NoSuchElementException("Start vertex not found");
+        
+        pq.add(new Path(start, 0));
+        start.dist = 0;
+        
+        int nodesSeen = 0;
+        while (!pq.isEmpty() && nodesSeen < vertexMap.size()) {
+            Path vrec = pq.remove();
+            Vertex v = vrec.dest;
+            if (v.visited != 0) // skip visited
+                continue;
+            
+            v.visited = 1; // set visited
+            nodesSeen++;
+            
+            for (Edge e : v.adj) {
+                Vertex w = e.dest;
+                double cvw = e.cost; // cost between v and w
+                if (cvw < 0) {
+                    // throw new GraphException("Graph has negative edges");
+                }
+                
+                if (w.dist > v.dist + cvw) {
+                    w.dist = v.dist + cvw;
+                    w.prev = v; // set previous Vertex
+                    pq.add(new Path(w, w.dist));
+                }
+            }
+        }
+    }
+    
+    class Vertex {
+        int visited;
+        Vertex prev;
+        double dist;
+        List<Edge> adj;
+    }
+    
+    class Edge {
+        Vertex dest;
+        double cost;
+    }
+}