fix: using single array instance

Author: ashokdey

src/_DataStructures_/Trees/BinarySearchTree/index.js

@@ -19,15 +19,15 @@ class BinarySearchTree {
   }
 
   preorder() {
-    return BSTUtils.preorder(this.root);
+    return BSTUtils.preorder(this.root, []);
   }
 
   postorder() {
-    return BSTUtils.postorder(this.root);
+    return BSTUtils.postorder(this.root, []);
   }
 
   inorder() {
-    return BSTUtils.inorder(this.root);
+    return BSTUtils.inorder(this.root, []);
   }
 
   search(value) {
@@ -70,7 +70,7 @@ class BinarySearchTree {
 // console.log('Postorder Traversal - ', postorder);
 
 // const search = 18;
-// console.log(`Search for ${search}`, bst.searchFor(search));
+// console.log(`Search for ${search}`, bst.search(search));
 
 // const minNode = bst.getMinimum();
 // console.log('Minimum value =>', minNode);

src/_DataStructures_/Trees/BinarySearchTree/utils.js

@@ -22,48 +22,28 @@ const utils = {
     }
   },
 
-  preorder(root) {
-    /** returning an array so as to make testing easy */
-    let arr = [];
-    if (root === null) return [];
-    arr.push(root.value);
-
-    const left = this.preorder(root.leftChild);
-    arr = [...arr, ...left];
-
-    const right = this.preorder(root.rightChild);
-    arr = [...arr, ...right];
-    return arr;
+  preorder(root, array) {
+    if (root === null) return array;
+    array.push(root.value);
+    this.preorder(root.leftChild, array);
+    this.preorder(root.rightChild, array);
+    return array;
   },
 
-  inorder(root) {
-    /** left - root - right */
-    if (root === null) return [];
-    let arr = [];
-    const left = this.inorder(root.leftChild);
-    arr = [...left, ...arr];
-
-    // print root
-    arr = [...arr, root.value];
-
-    const right = this.inorder(root.rightChild);
-    arr = [...arr, ...right];
-    return arr;
+  inorder(root, array) {
+    if (root === null) return array;
+    this.inorder(root.leftChild, array);
+    array.push(root.value);
+    this.inorder(root.rightChild, array);
+    return array;
   },
 
-  postorder(root) {
-    /** left - right - root */
-
-    if (root === null) return [];
-    let arr = [];
-
-    const left = this.postorder(root.leftChild);
-    arr = [...left, ...arr];
-
-    const right = this.postorder(root.rightChild);
-    arr = [...arr, ...right];
-
-    return [...arr, root.value];
+  postorder(root, array) {
+    if (root === null) return array;
+    this.postorder(root.leftChild, array);
+    this.postorder(root.rightChild, array);
+    array.push(root.value);
+    return array;
   },
 
   // eslint-disable-next-line consistent-return