fix(bst): on duplicates values the same node is returned

Fixesamejiarosario#99

Author: amejiarosario

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

@@ -19,23 +19,24 @@ class BinarySearchTree {
  * @returns {BinaryTreeNode} newly added node
  */
 add(value){
-constnewNode=newBinaryTreeNode(value);
+letnode=newBinaryTreeNode(value);
 
 if(this.root){
 const{ found, parent }=this.findNodeAndParent(value);// <1>
 if(found){// duplicated: value already exist on the tree
 found.meta.multiplicity=(found.meta.multiplicity||1)+1;// <2>
+node=found;
 }elseif(value<parent.value){
-parent.setLeftAndUpdateParent(newNode);
+parent.setLeftAndUpdateParent(node);
 }else{
-parent.setRightAndUpdateParent(newNode);
+parent.setRightAndUpdateParent(node);
 }
 }else{
-this.root=newNode;
+this.root=node;
 }
 
 this.size+=1;
-returnnewNode;
+returnnode;
 }
 // end::add[]
 

src/data-structures/trees/binary-search-tree.spec.js

@@ -66,7 +66,7 @@ describe('Binary Search Tree', () => {
 it('should deal with duplicates',()=>{
 constroot=bst.add(1);
 expect(root.meta.multiplicity).toBe(undefined);
-bst.add(1);
+expect(bst.add(1)).toBe(root);// should return existing
 expect(bst.size).toBe(2);
 expect(root.toValues()).toMatchObject({
 value: 1,parent: null,left: null,right: null,
@@ -262,7 +262,7 @@ describe('Binary Search Tree', () => {
 });
 
 it('should remove duplicates',()=>{
-bst.add(40);// add duplicate
+expect(bst.add(40)).toBe(n40);// add duplicate
 expect(n40.meta.multiplicity).toBe(2);
 
 expect(bst.remove(40)).toBe(true);