Merge pull request #13 from spencerking/binary_tree

Adding binary tree traversal and inversion

data_structures/binary_trees/inorder_traversal.rb

@@ -0,0 +1,23 @@
+# Definition for a binary tree node.
+# class TreeNode
+#     attr_accessor :val, :left, :right
+#     def initialize(val)
+#         @val = val
+#         @left, @right = nil, nil
+#     end
+# end
+
+# @param {TreeNode} root
+# @return {Integer[]}
+def inorder_traversal(root)
+    ans = []
+    def traverse(node, ans)
+        if node != nil
+            traverse(node.left, ans)
+            ans.push(node.val)
+            traverse(node.right,ans)
+        end
+    end
+    traverse(root,ans)
+    return ans
+end

data_structures/binary_trees/invert.rb

@@ -0,0 +1,20 @@
+# Definition for a binary tree node.
+# class TreeNode
+#     attr_accessor :val, :left, :right
+#     def initialize(val)
+#         @val = val
+#         @left, @right = nil, nil
+#     end
+# end
+
+# @param {TreeNode} root
+# @return {TreeNode}
+def invert_tree(root)
+    if root == nil
+        return nil
+    end
+    temp = root.left
+    root.left = invert_tree(root.right)
+    root.right = invert_tree(temp)
+    return root
+end

data_structures/binary_trees/postorder_traversal.rb

@@ -0,0 +1,23 @@
+# Definition for a binary tree node.
+# class TreeNode
+#     attr_accessor :val, :left, :right
+#     def initialize(val)
+#         @val = val
+#         @left, @right = nil, nil
+#     end
+# end
+
+# @param {TreeNode} root
+# @return {Integer[]}
+def postorder_traversal(root)
+    ans = []
+    def traverse(node, ans)
+        if node != nil
+            traverse(node.left, ans)
+            traverse(node.right,ans)
+            ans.push(node.val)
+        end
+    end
+    traverse(root,ans)
+    return ans
+end

data_structures/binary_trees/preorder_traversal.rb

@@ -0,0 +1,23 @@
+# Definition for a binary tree node.
+# class TreeNode
+#     attr_accessor :val, :left, :right
+#     def initialize(val)
+#         @val = val
+#         @left, @right = nil, nil
+#     end
+# end
+
+# @param {TreeNode} root
+# @return {Integer[]}
+def preorder_traversal(root)
+    ans = []
+    def traverse(node, ans)
+        if node != nil
+            ans.push(node.val)
+            traverse(node.left, ans)
+            traverse(node.right,ans)
+        end
+    end
+    traverse(root,ans)
+    return ans
+end