Merge pull request #180 from NimrodRak/master

Added Disjoint Sets Data Structure

data_structures/disjoint_sets/disjoint_sets.rb

@@ -0,0 +1,56 @@
+class Node
+    attr_accessor :data, :parent, :rank
+    def initialize(data)
+        @data = data
+        @parent = self
+        @rank = 0
+    end
+    def parent
+        @parent
+    end
+    def parent=(parent)
+        @parent = parent;
+    end
+    def rank
+        @rank
+    end
+    def rank=(rank)
+        @rank = rank
+    end
+end
+
+class DisjointSets
+    def make_set(d)
+        Node.new(d)
+    end
+
+    def find_set(x)
+        raise ArgumentError unless x.class <= Node
+        x.parent=(find_set(x.parent)) unless x.parent == x
+        x.parent
+    end
+
+    def union_set(x, y)
+        px = find_set(x)
+        py = find_set(y)
+        return if px == py
+        if px.rank > py.rank
+            py.parent = px
+        elsif py.rank > px.rank
+            px.parent = py
+        else
+            px.parent = py
+            py.rank += 1
+        end
+    end
+end
+
+ds = DisjointSets.new
+one = ds.make_set(1)
+two = ds.make_set(2)
+three = ds.make_set(3)
+ds.union_set(one, two)
+puts ds.find_set(one) == ds.find_set(two) # should be true
+ds.union_set(one, three)
+puts ds.find_set(two) == ds.find_set(three) # should be true
+puts one.rank + two.rank + three.rank == 1 # should be true