Add circular queue

data_structures/queues/circular_queue.rb

@@ -0,0 +1,72 @@
+class CircularQueue
+  def initialize(max_size)
+    @max_size = max_size
+    @queue = Array.new(max_size, nil)
+    @front = 0
+    @back = 0
+    @size = 0
+  end
+
+  attr_accessor :front, :back, :size
+  attr_reader :max_size, :queue
+
+  def empty?
+    size == 0
+  end
+
+  def peek
+    return nil if empty?
+
+    queue[front]
+  end
+
+  def add(x)
+    raise "Queue is at max capacity" if size == max_size
+
+
+    queue[back] = x
+    @back = (back + 1) % max_size
+    @size += 1
+  end
+
+  def pop
+    raise "Queue is empty" if size == 0
+
+    temp = queue[front]
+    queue[front] = nil
+    @front = (front + 1) % max_size
+    @size -= 1
+
+    temp
+  end
+end
+
+queue = CircularQueue.new(3)
+
+begin
+  queue.pop
+rescue => e
+  puts e.message
+end
+
+queue.add(1)
+queue.add(2)
+queue.add(3)
+
+begin
+  queue.add(4)
+rescue => e
+  puts e.message
+end
+
+puts queue.inspect
+# => #<CircularQueue:0x00007fea23876cd8 @max_size=3, @queue=[1, 2, 3], @front=0, @back=0, @size=3>
+
+puts queue.peek
+# => 1
+
+queue.pop
+
+puts queue.peek
+# => 2
+