problems: add insert-into-a-bst

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/insert-into-a-binary-search-tree.rb

@@ -0,0 +1,36 @@
+# Definition for a binary tree node.
+# class TreeNode
+#     attr_accessor :val, :left, :right
+#     def initialize(val = 0, left = nil, right = nil)
+#         @val = val
+#         @left = left
+#         @right = right
+#     end
+# end
+# @param {TreeNode} root
+# @param {Integer} val
+# @return {TreeNode}
+def insert_into_bst(root, val)
+    new_node = TreeNode.new(val)
+    if root == nil then
+        return new_node
+    end
+
+    node = root
+    while (val < node.val && node.left != nil) || (val >= node.val && node.right != nil) do
+        if val < node.val then
+            node = node.left
+        else
+            node = node.right
+        end
+    end
+
+    # insert the node
+    if val < node.val then
+        node.left = new_node
+    else
+        node.right = new_node
+    end
+
+    return root
+end