Add CoffeScript implementation

Author: Afnizar Nur Ghifari

dijkstras.coffee

@@ -0,0 +1,94 @@
+PriorityQueue = () ->
+  @_nodes = []
+  @enqueue = (priority, key) ->
+    @_nodes.push
+      key : key
+      priority : priority
+    @sort()
+    return
+  @dequeue = () ->
+    @_nodes.shift().key
+  @sort = () ->
+    @_nodes.sort = (a, b) ->
+      a.priority - b.priority
+    return
+  @isEmpty = () ->
+    !@_nodes.length
+  return
+
+Graph = ->
+  INFINITY = 1 / 0
+  @vertices = {}
+
+  @addVertex = (name, edges) ->
+    @vertices[name] = edges
+    return
+
+  @shortestPath = (start, finish) ->
+    nodes = new PriorityQueue
+    distances = {}
+    previous = {}
+    path = []
+    smallest = undefined
+    vertex = undefined
+    neighbor = undefined
+    alt = undefined
+
+    for vertex of @vertices
+      if vertex is start
+        distances[vertex] = 0
+        nodes.enqueue(0, vertex)
+      else
+        distances[vertex] = INFINITY
+        nodes.enqueue(INFINITY, vertex)
+      previous[vertex] = null
+
+    while not nodes.isEmpty()
+      smallest = nodes.dequeue()
+
+      if smallest is finish
+        path = []
+        while previous[smallest]
+          path.push smallest
+          smallest = previous[smallest]
+        break
+
+      if not smallest or distances[smallest] is INFINITY
+        continue
+      for neighbor of @vertices[smallest]
+        alt = distances[smallest] + @vertices[smallest][neighbor]
+        if alt < distances[neighbor]
+          distances[neighbor] = alt
+          previous[neighbor] = smallest
+          nodes.enqueue alt, neighbor
+    path
+  return
+
+g = new Graph()
+
+g.addVertex 'A',
+  B: 7
+  C: 8
+g.addVertex 'B',
+  A: 7
+  F: 2
+g.addVertex 'C',
+  A: 8
+  F: 6
+  G: 4
+g.addVertex 'D', F: 8
+g.addVertex 'E', H: 1
+g.addVertex 'F',
+  B: 2
+  C: 6
+  D: 8
+  G: 9
+  H: 3
+g.addVertex 'G',
+  C: 4
+  F: 9
+g.addVertex 'H',
+  E: 1
+  F: 3
+
+console.log g.shortestPath('A', 'H').concat([ 'A' ]).reverse()