Branches - Caroline

lib/dijkstra.rb

@@ -1,12 +1,112 @@
+##### I'M LEAVING IN MY PRINT STATEMENTS BC IT HELPS ME REMEMBER WHY I DID WHAT I DID...
 
 def dijkstra(adjacency_matrix, start_node) 
-
+
+  puts "==============\nADJACENCY MATRIX"
+  adjacency_matrix.each do |r|
+    p r
+  end
+  puts "==============\n\n"
+
+
   #int nVertices = adjacencyMatrix[0].length; 
   num_nodes = adjacency_matrix.length
-
+  
   # shortest_distances will hold the shortest distances from start_node to i
   # it starts with infinity as the value
   shortest_distances = Array.new(num_nodes, Float::INFINITY)
+  immedParent = Array.new(num_nodes, nil)
+  visited = Array.new(num_nodes, false)
+
+  # set up for the starter node
+  visited[start_node] = true
+  immedParent[start_node] = nil
+  shortest_distances[start_node] = 0
+  currNode = start_node
+
+  processCurrNode(adjacency_matrix[currNode], currNode, shortest_distances, immedParent, visited)
+
+  while keepVisiting(visited)
+    puts "keep visiting!"
+
+    currNode = getNextToVisit(visited, shortest_distances)
+    if !currNode 
+      # ran out of available next neighbors, but we haven't visited almost everyone (only 1 is allowed to be unvisited) yet!
+      break
+    end
+
+    visited[currNode] = true 
+
+    processCurrNode(adjacency_matrix[currNode], currNode, shortest_distances, immedParent, visited)
+
+  end
+
+
+  puts "GRAND FINALE"
+  puts "\tvisited = #{visited.inspect}"
+  puts "\timmedParent = #{immedParent.inspect}"
+  puts "\tshortestDistances = #{shortest_distances.inspect}\n"
+
+  answer = {
+    start_node: start_node, 
+    parent_list: immedParent, 
+    shortest_distances: shortest_distances
+  }
+
+  return answer
+end
 
+def keepVisiting(visited)
+  return visited.count(false) != 1
+end
 
+def getNextToVisit(visited, shortest_distances)
+  shortest = Float::INFINITY
+  winner = nil
+
+  visited.each_with_index do |visitedStatus, i|
+    puts "looking at... visitedStatus=#{visitedStatus} for node #{i}"
+    if visitedStatus == false && shortest_distances[i] < shortest
+      winner = i 
+      shortest = shortest_distances[i]
+    end
+  end
+
+  if winner
+    puts "\nNext up is... node #{winner}, it's distance is #{shortest}\n"
+    return winner 
+  else
+    return nil
+  end
 end
+
+def processCurrNode(currNodesDistances, currNode, shortest_distances, immedParent, visited)
+  puts "Processing... #{currNodesDistances.inspect}"
+
+  currNodesDistances.each_with_index do |distance, destinationNode|
+    puts "looking at #{distance} for nodeIndex #{destinationNode}"
+    if visited[destinationNode]
+      # puts "already visited this node, including self"
+      next
+    elsif distance == 0
+      # puts "this node is defined as not reachable"
+      next
+    else 
+      # puts "is this new distance shorter?"
+      recordedSD = shortest_distances[destinationNode]
+      prevLeg = shortest_distances[currNode]
+      currDistance = distance + prevLeg
+
+      if currDistance < recordedSD
+        puts "\tfound a shorter distance!"
+        shortest_distances[destinationNode] = currDistance
+        immedParent[destinationNode] = currNode
+      end
+    end
+  end
+
+  puts "Ended with..."
+  puts "\tvisited = #{visited.inspect}"
+  puts "\timmedParent = #{immedParent.inspect}"
+  puts "\tshortestDistances = #{shortest_distances.inspect}\n"
+end