Dijkstra Algorithm in Ruby (#935)

Dijkstra_Algorithm/Dijkstra_Algorithm.rb

@@ -0,0 +1,71 @@
+LONG_INT_MAX = 1 << 64 - 1
+
+def dijkstra(graph, source)
+    number_vertex = graph.length
+
+    # array that will store cost to vertices from source vertex
+    distance = Array.new(number_vertex, LONG_INT_MAX)
+
+    # array that shows vertices that are included in the shortest path tree
+    shortest_path_tree = Array.new(number_vertex, false)
+    distance[source] = 0
+
+    for i in 0..number_vertex-1
+
+        # finding vertex with shortest path from source vertex that is not shortest path tree
+        pivot = -1
+        for j in 0..number_vertex-1
+            if shortest_path_tree[j] == false and (pivot == -1 or distance[j] < distance[pivot]) then
+                pivot = j
+            end
+        end
+        # include found vertex to the shortes path tree
+        shortest_path_tree[pivot] = true
+
+        # updating the weights of all adjacent vertices with 'pivot' vertex 
+        for vertex in 0..number_vertex-1
+            if shortest_path_tree[vertex] == false && graph[pivot][vertex] != 0 &&
+                distance[pivot] + graph[pivot][vertex] < distance[vertex] then
+                distance[vertex] = distance[pivot] + graph[pivot][vertex]            
+            end
+        end                  
+    end
+
+    puts "Distance from Source:"
+    puts "Vertex\t\tDistance"
+    for i in 0..number_vertex-1
+        print i, "\t\t", distance[i], "\n"
+    end
+end
+
+# creating 10x10 weight matrix for graph
+graph = [[0, 14, 0, 7, 0, 0, 0, 8, 0, 10],
+        [14, 0, 8, 0, 0, 0, 0, 11, 0, 0],
+        [0, 8, 0, 7, 0, 4, 0, 0, 2, 0],
+        [7, 0, 7, 0, 9, 12, 0, 0, 0, 5],
+        [0, 0, 0, 9, 0, 0, 0, 0, 0, 0],
+        [0, 0, 4, 0, 0, 0, 2, 0, 0, 11],
+        [0, 0, 0, 12, 0, 2, 0, 1, 6, 15],
+        [8, 11, 0, 0, 0, 0, 1, 0, 7, 0],
+        [0, 0, 2, 0, 0, 0, 6, 7, 0, 0],
+        [10, 0, 0, 5, 0, 11, 15, 0, 0, 0]]
+
+dijkstra(graph, 0);
+
+=begin Output
+
+    Distance from Source:
+    Vertex		Distance
+    0		0
+    1		14
+    2		14
+    3		7
+    4		16
+    5		11
+    6		9
+    7		8
+    8		15
+    9		10
+
+=end
+