Add binary search tree.

src/data-structures/tree/BinaryTreeNode.js

@@ -1,17 +1,20 @@
 export default class BinaryTreeNode {
-  constructor(value = null) {
+  constructor(value = null, parent = null) {
     this.left = null;
     this.right = null;
+    this.parent = parent;
     this.value = value;
   }
 
   setLeft(node) {
     this.left = node;
+    this.left.parent = this;
     return this;
   }
 
   setRight(node) {
     this.right = node;
+    this.right.parent = this;
     return this;
   }
 

src/data-structures/tree/__test__/BinaryTreeNode.test.js

@@ -23,6 +23,21 @@ describe('BinaryTreeNode', () => {
     expect(rootNode.right.value).toBe(3);
   });
 
+  it('should set parent', () => {
+    const leftNode = new BinaryTreeNode(1);
+    const rightNode = new BinaryTreeNode(3);
+    const rootNode = new BinaryTreeNode(2);
+
+    rootNode
+      .setLeft(leftNode)
+      .setRight(rightNode);
+
+    expect(rootNode.parent).toBeNull();
+    expect(rootNode.left.parent.value).toBe(2);
+    expect(rootNode.right.parent.value).toBe(2);
+    expect(rootNode.right.parent).toEqual(rootNode);
+  });
+
   it('should traverse node', () => {
     const leftNode = new BinaryTreeNode(1);
     const rightNode = new BinaryTreeNode(3);

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

@@ -14,7 +14,7 @@ export default class BinarySearchTree {
   }
 
   remove(value) {
-    const nodeToRemove = this.findNode(value);
+    const nodeToRemove = this.root.find(value);
 
     if (!nodeToRemove) {
       throw new Error('Item not found in the tree');

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

@@ -12,14 +12,14 @@ export default class BinarySearchTreeNode extends BinaryTreeNode {
       if (this.left) {
         this.left.insert(value);
       } else {
-        this.left = new BinarySearchTreeNode(value);
+        this.setLeft(new BinarySearchTreeNode(value));
       }
     } else if (value > this.value) {
       // Insert to the right.
       if (this.right) {
         this.right.insert(value);
       } else {
-        this.right = new BinarySearchTreeNode(value);
+        this.setRight(new BinarySearchTreeNode(value));
       }
     }