add delete_node_in_a_bst onn ruby version

August-LeetCoding-Challenge/31-Delete-Node-in-a-BST/Delete-Node-in-a-BST.rb

@@ -0,0 +1,49 @@
+# 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} key
+# @return {TreeNode}
+def delete_node(root, key)
+    if root == nil 
+        return root
+    elsif root.val > key
+        root.left = delete_node(root.left, key)
+
+    elsif root.val < key
+        root.right = delete_node(root.right, key)
+
+    else
+        if root.left == nil && root.right == nil
+            root = nil
+            return nil
+        elsif root.left == nil
+            tmp = root.right
+            root = nil
+            return tmp
+        elsif root.right == nil
+            tmp = root.left 
+            root = nil
+            return tmp
+        else
+            tmp = min_value(root.right)
+            root.val = tmp.val
+            root.right = delete_node(root.right, tmp.val)
+        end
+    end
+    return root
+end
+
+def min_value(node)
+    current = node
+    while current.left != nil
+        current = current.left 
+    end
+    current
+end