Shubha 🦄

lib/tree.rb

@@ -16,47 +16,131 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(h), where h is the maximum height of the binary tree. 
+  # In a balanced tree, this would be O(log n)
+  # Space Complexity: O(1), the method will always create one(1) new node
   def add(key, value)
-    raise NotImplementedError
+    new_node = TreeNode.new(key, value)
+    if !@root
+      @root = new_node
+      return
+    end
+    current = @root
+    while current
+      if key <= current.key
+        if current.left
+          current = current.left
+        else
+          current.left = new_node
+          break
+        end
+      else
+        if current.right
+          current = current.right
+        else
+          current.right = new_node
+          break
+        end
+      end
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(h), where h is the maximum height of the binary tree. 
+  # In a balanced tree, this would be O(log n)
+  # Space Complexity: O(1), no new nodes are created
   def find(key)
-    raise NotImplementedError
+    current = @root
+    while current
+      if key == current.key
+        return current.value
+      elsif key < current.key
+        current = current.left
+      else
+        current = current.right
+      end
+    end
+    return
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n) where n is the number of nodes
+  # Space Complexity: O(n) where n is the number of nodes
   def inorder
-    raise NotImplementedError
+    nodes = []
+    if @root
+      add_nodes_inorder(root, nodes)
+    end
+    return nodes
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def add_nodes_inorder(node, array)
+    return if !node
+    add_nodes_inorder(node.left, array)
+    array << { key: node.key, value: node.value }
+    add_nodes_inorder(node.right, array)
+  end
+
+  # Time Complexity: O(n) where n is the number of nodes
+  # Space Complexity: O(n) where n is the number of nodes
   def preorder
-    raise NotImplementedError
+    nodes = []
+    if @root
+      add_nodes_preorder(root, nodes)
+    end
+    return nodes
+  end
+
+  def add_nodes_preorder(node, array)
+    return if !node
+    array << { key: node.key, value: node.value }
+    add_nodes_preorder(node.left, array)
+    add_nodes_preorder(node.right, array)   
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n) where n is the number of nodes
+  # Space Complexity: O(n) where n is the number of nodes
   def postorder
-    raise NotImplementedError
+    nodes = []
+    if @root
+      add_nodes_postorder(root, nodes)
+    end
+    return nodes
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def add_nodes_postorder(node, array)
+    return if !node
+    add_nodes_postorder(node.left, array)
+    add_nodes_postorder(node.right, array)   
+    array << { key: node.key, value: node.value }
+  end
+
+  # Time Complexity: O(n) where n is the number of nodes
+  # Space Complexity: O(n) where n is the number of nodes
   def height
-    raise NotImplementedError
+    return max_depth(@root)
   end
 
+  def max_depth(node)
+    return 0 if !node
+    right = max_depth(node.right)
+    left = max_depth(node.left)
+    return [right, left].max + 1
+  end
   # Optional Method
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n) where n is the number of nodes
+  # Space Complexity: O(n) where n is the number of nodes
   def bfs
-    raise NotImplementedError
+    return [] if !@root
+    queue = []
+    nodes = []
+
+    queue.push(@root)
+    while !queue.empty?
+      current = queue.shift
+      nodes << { key: current.key, value: current.value }
+      queue.push(current.left) if current.left
+      queue.push(current.right) if current.right
+    end
+    return nodes
   end
 
   # Useful for printing

test/tree_test.rb

@@ -69,6 +69,16 @@
     end
   end
 
+  describe "height" do
+    it "will return 0 for an empty tree" do
+      expect(tree.height).must_equal 0
+    end
+
+    it "will return the number of edges from the root to the deepest leaf" do
+      expect(tree_with_nodes.height).must_equal 4
+    end
+  end
+
   describe "breadth first search" do
     it "will give an empty array for an empty tree" do
       expect(tree.bfs).must_equal []