Remove parent parameter from binary tree node constructor to simplify syntax.

Author: trekhleb

src/data-structures/tree/BinaryTreeNode.js

@@ -3,12 +3,11 @@ import Comparator from '../../utils/comparator/Comparator';
 export default class BinaryTreeNode {
   /**
    * @param {*} [value]
-   * @param {BinaryTreeNode} [parent]
    */
-  constructor(value = null, parent = null) {
+  constructor(value = null) {
     this.left = null;
     this.right = null;
-    this.parent = parent;
+    this.parent = null;
     this.value = value;
 
     // This comparator is used to compare binary tree nodes with each other.

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

@@ -6,7 +6,7 @@ export default class BinarySearchTree {
    */
   constructor(nodeValueCompareFunction) {
     this.nodeValueCompareFunction = nodeValueCompareFunction;
-    this.root = new BinarySearchTreeNode(null, null, this.nodeValueCompareFunction);
+    this.root = new BinarySearchTreeNode(null, this.nodeValueCompareFunction);
   }
 
   /**

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

@@ -4,11 +4,10 @@ import Comparator from '../../../utils/comparator/Comparator';
 export default class BinarySearchTreeNode extends BinaryTreeNode {
   /**
    * @param {*} [value]
-   * @param {BinaryTreeNode} [parent]
    * @param {function} [compareFunction]
    */
-  constructor(value = null, parent = null, compareFunction = undefined) {
-    super(value, parent);
+  constructor(value = null, compareFunction = undefined) {
+    super(value);
 
     // This comparator is used to compare node values with each other.
     this.compareFunction = compareFunction;
@@ -30,14 +29,14 @@ export default class BinarySearchTreeNode extends BinaryTreeNode {
       if (this.left) {
         this.left.insert(value);
       } else {
-        this.setLeft(new BinarySearchTreeNode(value, null, this.compareFunction));
+        this.setLeft(new BinarySearchTreeNode(value, this.compareFunction));
       }
     } else if (this.nodeValueComparator.greaterThan(value, this.value)) {
       // Insert to the right.
       if (this.right) {
         this.right.insert(value);
       } else {
-        this.setRight(new BinarySearchTreeNode(value, null, this.compareFunction));
+        this.setRight(new BinarySearchTreeNode(value, this.compareFunction));
       }
     }
 

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

@@ -188,7 +188,7 @@ describe('BinarySearchTreeNode', () => {
     const obj2 = { key: 'obj2', value: 2, toString: () => 'obj2' };
     const obj3 = { key: 'obj3', value: 3, toString: () => 'obj3' };
 
-    const bstNode = new BinarySearchTreeNode(obj2, null, nodeValueComparatorCallback);
+    const bstNode = new BinarySearchTreeNode(obj2, nodeValueComparatorCallback);
     bstNode.insert(obj1);
 
     expect(bstNode.toString()).toBe('obj1,obj2');