Commit efd1414

@@ -1,48 +0,0 @@
-<<-DOC
-You are given a single linked list, and you are asked to determine if there is a circle inside it
-A circle means, a -> b -> c -> b, then it is a circle
-
-Part 2.
-Could you get the length of the circle for the input single linked list if there is one, or output 0 if there is no circle? (O(1) space and O(n) time complexity)
-
-DOC
-require 'byebug'
-
-def circle?(head)
-  return false if head.nil?
-
-  tortoise, hare = head, head.next_item
-
-  until hare.nil?
-    return true if tortoise == hare
-    tortoise, hare = tortoise.next_item, hare.next_item&.next_item
-  end
-
-  false
-end
-
-class Node
-  attr_reader :next_item, :value
-
-  def initialize(value)
-    @value = value
-  end
-
-  def add(value)
-    @next_item = value.is_a?(Node) ? value : Node.new(value)
-  end
-
-  def inspect
-    "#{object_id} #{value}"
-  end
-end
-
-a = Node.new("A")
-b = Node.new("B")
-c = Node.new("C")
-
-a.add(b)
-b.add(c)
-c.add(b)
-
-raise 'heck' unless circle?(a)

@@ -0,0 +1,112 @@
+<<-DOC
+You are given a single linked list, and you are asked to determine if there is a circle inside it
+A circle means, a -> b -> c -> b, then it is a circle
+
+Part 2.
+Could you get the length of the circle for the input single linked list if there is one, 
+or output 0 if there is no circle? (O(1) space and O(n) time complexity)
+
+A -> B -> C -> D -> E -> F -> D
+|T|H|
+|A|B|
+|B|D|
+|C|F|
+|D|E|
+|E|D|
+
+
+DOC
+require 'spec_helper'
+describe "cycle" do
+
+
+  def circle?(head)
+    return false if head.nil?
+
+    tortoise, hare = head, head.next_item
+
+    until hare.nil?
+      return true if tortoise == hare
+      tortoise, hare = tortoise.next_item, hare.next_item&.next_item
+    end
+
+    false
+  end
+
+  def cycle_length(head)
+    return 0 if head.nil?
+
+    tortoise, hare = head, head.next_item
+
+    detected = false
+    count = 0
+
+    until hare.nil?
+      if tortoise == hare
+        return count if detected
+        detected = true
+      end
+      count += 1 if detected
+      tortoise, hare = tortoise.next_item, hare.next_item&.next_item
+    end
+    0
+  end
+
+  class Node
+    attr_reader :next_item, :value
+
+    def initialize(value)
+      @value = value
+    end
+
+    def add(value)
+      @next_item = value.is_a?(Node) ? value : Node.new(value)
+    end
+
+    def inspect
+      "#{object_id} #{value}"
+    end
+  end
+
+  it do
+    a = Node.new("A")
+    b = Node.new("B")
+    c = Node.new("C")
+
+    a.add(b)
+    b.add(c)
+    c.add(b)
+    expect(circle?(a)).to be_truthy
+    expect(cycle_length(a)).to eql(2)
+  end
+
+
+  <<-DOC
+A -> B -> C -> D -> E -> F -> D
+
+|T|H|
+|A|B|
+|B|D|
+|C|F|
+|D|E|
+|E|D|
+  DOC
+
+  it do
+    a = Node.new("A")
+    b = Node.new("B")
+    c = Node.new("C")
+    d = Node.new("D")
+    e = Node.new("E")
+    f = Node.new("F")
+
+    a.add(b)
+    b.add(c)
+    c.add(b)
+    d.add(e)
+    e.add(f)
+    f.add(d)
+
+    expect(cycle_length(a)).to eql(3)
+  end
+end