Added a single linked list data structure

data_structures/LinkedLists/SingleList.rb

@@ -0,0 +1,80 @@
+# Define a node in the list
+class Node
+  attr_accessor :value, :next
+  def initialize(value)
+    @value = value
+    @next = nil
+  end
+end
+
+# A Class for single linked lists (each element links to the next one, but not to the previous one)
+
+class SingleList
+  attr_accessor :head
+  def initialize()
+    @head = nil
+  end
+
+  def insert_tail(value)
+    newNode = Node.new(value)
+    if (@head == nil)
+      @head = newNode
+    else
+      tempNode = @head
+      while (tempNode.next != nil)
+        tempNode = tempNode.next
+      end
+      tempNode.next = newNode
+    end
+  end
+
+  def insert_head(value)
+    newNode = Node.new(value)
+    if (@head == nil)
+      @head = newNode
+    else
+      newNode.next = @head
+      @head = newNode
+    end
+  end
+
+  def print_list()
+    print "["
+    if (@head != nil)
+      printNode = @head
+      while (printNode != nil)
+        print "#{printNode.value}"
+        if (printNode.next != nil)
+          print ", "
+        end
+        printNode = printNode.next
+      end
+    end
+    print "]"
+    STDOUT.flush
+  end
+
+  def delete_head
+    if (@head != nil) && (@head.next != nil)
+      newHead = @head.next
+      @head = newHead
+    elsif (@head != nil) && (@head.next == nil)
+      @head = nil
+    end
+  end
+
+  def delete_tail
+    if (@head != nil)
+      tempNode = @head
+      while (tempNode.next.next != nil)
+        tempNode = tempNode.next
+      end
+      tempNode.next = nil
+    end
+  end
+
+  def isEmpty()
+    return (@head==nil)
+  end
+
+end