completed part 1-4

tree-practice.rb

@@ -5,6 +5,7 @@ def initialize(val)
      @value = val
      @left = nil
      @right = nil
+     @count = 0
    end
 end
 
@@ -15,7 +16,69 @@ def print_infix(node)
   print_infix(node.right)
 end
 
-root = TreeNode.new("+")
-root.left = TreeNode.new("3")
-root.right = TreeNode.new("2")
-print_infix(root)
+# part 1
+def operators(node)
+  return if node == nil
+  operators(node.left)
+  if node.left != nil || node.right != nil
+    print node.value + " "
+  end
+  operators(node.right)
+end
+
+# part 2
+def countnonops(node, count = 0)
+  if node.left == nil && node.right == nil
+    return 1
+  else
+    countnonops(node.left, count += 1) + countnonops(node.right, count += 1)
+  end
+end
+
+# part 3
+def prefix(node)
+  return if node == nil
+  print node.value + " "
+  prefix(node.left)
+  prefix(node.right)
+end
+
+def postfix(node)
+  return if node == nil
+  postfix(node.left)
+  postfix(node.right)
+  print node.value + " "
+end
+
+# part 4
+def find_op(node, operator)
+  if node.value == operator && node.value.match(/\D/) != nil
+    return true
+  elsif node.left != nil || node.right != nil
+    find_op(node.left, operator)
+    find_op(node.right, operator)
+  else
+    return false
+  end
+end
+
+root = TreeNode.new("-")
+root.right = TreeNode.new("%")
+root.right.left = TreeNode.new("10")
+root.right.right = TreeNode.new("5")
+root.left = TreeNode.new("+")
+root.left.right = TreeNode.new("2")
+root.left.left = TreeNode.new("*")
+root.left.left.left = TreeNode.new("4")
+root.left.left.right = TreeNode.new("3")
+puts print_infix(root)
+puts operators(root)
+puts countnonops(root)
+puts prefix(root)
+puts postfix(root)
+puts "find_op should return false"
+puts find_op(root, ")")
+puts "find_op should return true"
+puts find_op(root, "-")
+puts "find_op should ignore digit input and return false"
+puts find_op(root, "9")