FIRE - Tram

lib/possible_bipartition.rb

@@ -1,4 +1,39 @@
-
+# Time complexity:O(n) - visiting each node in the graph once, searching in sets is O(1)
+# Space complexity: O(n) - the sets can be filled up based on the content of the dislikes
+require 'set'
 def possible_bipartition(dislikes)
-  raise NotImplementedError, "possible_bipartition isn't implemented yet"
+  return true if dislikes.empty?
+  group_a, group_b, blocked_a, blocked_b = Set.new, Set.new, Set.new, Set.new
+
+  # if this index is not included in blocked_a, and go to the index in the adjacency list, and check if its dislikes are in not in group_a
+  # check if this index is not included in blocked_b, proceed
+    # go to the index and check if its dislikes are not in group_b
+  # return false if all four checks failed 
+  queue = [ 0 ]
+  queue << 1 if dislikes[0].empty?
+
+  until queue.empty?
+    puppy = queue.shift
+    if !blocked_a.include?(puppy) && group_a.intersection(dislikes[puppy]).empty?
+      # add puppy to group_a 
+      group_a << puppy
+      # add it's dislikes to blocked_a
+      dislikes[puppy].each { |dislike| blocked_a << dislike }
+    elsif !blocked_b.include?(puppy) && group_b.intersection(dislikes[puppy]).empty?
+      group_b << puppy
+      dislikes[puppy].each { |dislike| blocked_b << dislike }
+    else
+      return false
+    end
+
+    # place each of puppy's dislikes into queue if they're not in group_a or group_b
+    # if they're in group_a or group_b, it means that node has been visted
+    dislikes[puppy].each do |dislike|
+      if !(group_a + group_b).include?(dislike)
+        queue << dislike
+      end
+    end
+  end
+
+  true
 end