Homework for Binary Tree Expressions

README.md

@@ -1,7 +1,7 @@
 # Tree Practice
 
-## Creating a binary tree on paper
-On paper, create a binary search tree to represent the expressions below.
+## Creating a binary expression tree on paper
+On paper, create a binary expression tree to represent the expressions below.
 1. `3 + 2`
 2. `3 + 2 - 10`
 3. `4 * 3 + 2`

tree-practice.rb

@@ -1,21 +1,96 @@
 class TreeNode
-   attr_accessor :value, :left, :right
-
+  attr_accessor :value, :left, :right, :operator
    def initialize(val)
      @value = val
      @left = nil
      @right = nil
+     @operator = operator
    end
 end
 
+# evaluates left middle right
 def print_infix(node)
   return if node == nil
   print_infix(node.left)
   print node.value + " "
   print_infix(node.right)
 end
 
-root = TreeNode.new("+")
-root.left = TreeNode.new("3")
-root.right = TreeNode.new("2")
-print_infix(root)
+# evaluates middle left right
+def print_prefix(node)
+  return if node == nil
+  print node.value + " "
+  print_prefix(node.left)
+  print_prefix(node.right)
+end
+
+# evaluates left right middle
+def print_postfix(node)
+  return if node == nil
+  print_postfix(node.left)
+  print_postfix(node.right)
+  print node.value + " "
+end
+
+def print_operators(node)
+  return if node == nil
+  print_operators(node.left)
+  if node.left != nil || node.right != nil
+    print node.value + " "
+  end 
+  print_operators(node.right)
+end
+
+def print_non_operators(node)
+  return if node == nil
+  print_non_operators(node.left)
+  if node.left == nil || node.right == nil
+    print node.value + " "
+  end 
+  print_non_operators(node.right)
+end 
+
+def find_operators(node, operator)
+  return if node == nil
+  count = 0 
+  find_operators(node.left)
+  #  search the whole tree and count up the operators
+  if node.value == operator
+    count += 1
+  end
+  find_operators(node.right)
+end 
+
+# root = TreeNode.new("+")
+# root.left = TreeNode.new("3")
+# root.right = TreeNode.new("2")
+# puts print_infix(root)
+
+# root = TreeNode.new("-")
+# root.left = TreeNode.new("+")
+# root.right = TreeNode.new("10")
+# root.left.left = TreeNode.new("3")
+# root.left.right = TreeNode.new("2")
+
+# root = TreeNode.new("+")
+# root.left = TreeNode.new("*")
+# root.right = TreeNode.new("2")
+# root.left.left = TreeNode.new("4")
+# root.left.right = TreeNode.new("3")
+# puts print_infix(root)
+
+root = TreeNode.new("-")
+root.left = TreeNode.new("+")
+root.right = TreeNode.new("%")
+root.right.left = TreeNode.new("10")
+root.right.right = TreeNode.new("5")
+root.left.left = TreeNode.new("*")
+root.left.right = TreeNode.new("2")
+root.left.left.left = TreeNode.new("4")
+root.left.left.right = TreeNode.new("3")
+
+
+
+
+
+

tree-practice_test.rb

@@ -0,0 +1,37 @@
+gem 'minitest', '>= 5.0.0'
+require 'minitest/pride'
+require 'minitest/autorun'
+require_relative 'tree-practice'
+
+
+class TreeTest < Minitest::Test
+    @expression = TreeNode.new("-")
+    @expression.left = TreeNode.new("+")
+    @expression.right = TreeNode.new("%")
+    @expression.right.left = TreeNode.new("10")
+    @expression.right.right = TreeNode.new("5")
+    @expression.left.left = TreeNode.new("*")
+    @expression.left.right = TreeNode.new("2")
+    @expression.left.left.left = TreeNode.new("4")
+    @expression.left.left.right = TreeNode.new("3")
+
+  def test_infix_notation
+    assert_equal print_infix(@expression) "4 * 3 + 2 - 10 % 5"
+  end 
+
+  def test_postfix_notation
+    assert_equal print_postfix(@expression), '4 3 * 2 + 10 5 % -'
+  end
+
+  def test_prefix_notation
+    assert_equal print_prefix(@expression), '- + * 4 3 2 % 10 5'
+  end 
+
+  def test_print_operators
+    assert_equal print_operators(@expression), '* + - %'
+  end
+
+  def test_print_nonoperators
+    assert_equal print_non_operators(@expression), '4 3 2 10 5'
+  end
+end