Merge pull request amejiarosario#100 from amejiarosario/fix/nadhem-findings

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

Author: amejiarosario

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

@@ -19,23 +19,24 @@ class BinarySearchTree {
    * @returns {BinaryTreeNode} newly added node
    */
   add(value) {
-    const newNode = new BinaryTreeNode(value);
+    let node = new BinaryTreeNode(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;
       } else if (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;
-    return newNode;
+    return node;
   }
   // end::add[]
 

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

@@ -66,7 +66,7 @@ describe('Binary Search Tree', () => {
       it('should deal with duplicates', () => {
         const root = 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);