Fix issue trekhleb#98.

Author: trekhleb

src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js

@@ -132,6 +132,9 @@ export default class BinarySearchTreeNode extends BinaryTreeNode {
       }
     }
 
+    // Clear the parent of removed node.
+    nodeToRemove.parent = null;
+
     return true;
   }
 

src/data-structures/tree/binary-search-tree/__test__/BinarySearchTreeNode.test.js

@@ -243,4 +243,13 @@ describe('BinarySearchTreeNode', () => {
 
     expect(bstNode.findMin().value).toEqual(obj1);
   });
+
+  it('should abandon removed node', () => {
+    const rootNode = new BinarySearchTreeNode('foo');
+    rootNode.insert('bar');
+    const childNode = rootNode.find('bar');
+    rootNode.remove('bar');
+
+    expect(childNode.parent).toBeNull();
+  });
 });