Make it possible to insert meta information to bst node.

Author: trekhleb

src/data-structures/tree/BinaryTreeNode.js

@@ -5,7 +5,7 @@ export default class BinaryTreeNode {
    * @param {*} [value] - node value.
    * @param {Object} meta - any meta information that needs to be attached to the node.
    */
-  constructor(value = null, meta = {}) {
+  constructor(value = null, meta = null) {
     this.left = null;
     this.right = null;
     this.parent = null;

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

@@ -5,7 +5,7 @@ export default class BinarySearchTree {
    * @param {function} [nodeValueCompareFunction]
    */
   constructor(nodeValueCompareFunction) {
-    this.root = new BinarySearchTreeNode(null, nodeValueCompareFunction);
+    this.root = new BinarySearchTreeNode(null, null, nodeValueCompareFunction);
   }
 
   /**

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

@@ -3,11 +3,12 @@ import Comparator from '../../../utils/comparator/Comparator';
 
 export default class BinarySearchTreeNode extends BinaryTreeNode {
   /**
-   * @param {*} [value]
-   * @param {function} [compareFunction]
+   * @param {*} [value] - node value.
+   * @param {Object} [meta] - any meta information that is attached to the node.
+   * @param {function} [compareFunction] - comparator function for node values.
    */
-  constructor(value = null, compareFunction = undefined) {
-    super(value);
+  constructor(value = null, meta = null, compareFunction = undefined) {
+    super(value, meta);
 
     // This comparator is used to compare node values with each other.
     this.compareFunction = compareFunction;
@@ -16,27 +17,30 @@ export default class BinarySearchTreeNode extends BinaryTreeNode {
 
   /**
    * @param {*} value
+   * @param {Object} [meta]
    * @return {BinarySearchTreeNode}
    */
-  insert(value) {
+  insert(value, meta = null) {
     if (this.nodeValueComparator.equal(this.value, null)) {
       this.value = value;
+      this.meta = meta;
+
       return this;
     }
 
     if (this.nodeValueComparator.lessThan(value, this.value)) {
       // Insert to the left.
       if (this.left) {
-        this.left.insert(value);
+        this.left.insert(value, meta);
       } else {
-        this.setLeft(new BinarySearchTreeNode(value, this.compareFunction));
+        this.setLeft(new BinarySearchTreeNode(value, meta, this.compareFunction));
       }
     } else if (this.nodeValueComparator.greaterThan(value, this.value)) {
       // Insert to the right.
       if (this.right) {
-        this.right.insert(value);
+        this.right.insert(value, meta);
       } else {
-        this.setRight(new BinarySearchTreeNode(value, this.compareFunction));
+        this.setRight(new BinarySearchTreeNode(value, meta, this.compareFunction));
       }
     }
 

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

@@ -79,6 +79,23 @@ describe('BinarySearchTreeNode', () => {
     expect(node.findMin().value).toBe(1);
   });
 
+  it('should be possible to attach meta information to binary search tree nodes', () => {
+    const node = new BinarySearchTreeNode(10, { value: 10 });
+
+    node.insert(20, { value: 20 });
+    node.insert(30, { value: 30 });
+    node.insert(5, { value: 5 });
+    node.insert(40, { value: 40 });
+    node.insert(1, { value: 1 });
+
+    expect(node.meta.value).toBe(10);
+
+    expect(node.findMin()).not.toBeNull();
+    expect(node.findMin().value).toBe(1);
+    expect(node.findMin().meta.value).toBe(1);
+    expect(node.find(30).meta.value).toBe(30);
+  });
+
   it('should find node', () => {
     const node = new BinarySearchTreeNode(10);
 
@@ -188,7 +205,7 @@ describe('BinarySearchTreeNode', () => {
     const obj2 = { key: 'obj2', value: 2, toString: () => 'obj2' };
     const obj3 = { key: 'obj3', value: 3, toString: () => 'obj3' };
 
-    const bstNode = new BinarySearchTreeNode(obj2, nodeValueComparatorCallback);
+    const bstNode = new BinarySearchTreeNode(obj2, null, nodeValueComparatorCallback);
     bstNode.insert(obj1);
 
     expect(bstNode.toString()).toBe('obj1,obj2');