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Commit f920a4f

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Merge pull request knaxus#127 from k88manish/master
Implement Binary Tree to Binary Search Tree Conversion - Solution
2 parents a83dd6f + 7578fb1 commit f920a4f

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‎src/_DataStructures_/Trees/BinaryTree/index.js‎

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Original file line numberDiff line numberDiff line change
@@ -3,14 +3,14 @@ const Node = require('./Node');
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class BinaryTree {
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constructor(arr) {
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if (!Array.isArray(arr) || !arr.length) {
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throw new Error('Invalid argument to create a Binary Tre');
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throw new Error('Invalid argument to create a Binary Tree');
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}
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this.root = this.createBinaryTree((this.root = null), arr, 0);
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}
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// eslint-disable-next-line class-methods-use-this
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createBinaryTree(root, arr, i) {
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if (i < arr.length) {
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if (i < arr.length&&arr[i]) {
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// eslint-disable-next-line no-param-reassign
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root = new Node(arr[i]);
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// eslint-disable-next-line no-param-reassign
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const { binaryTreeToBST, storeInorder } = require('.');
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const BinaryTree = require('../../_DataStructures_/Trees/BinaryTree');
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describe('Binary tree to binary search tree', () => {
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let tree;
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describe('Create Binary Tree', () => {
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tree = new BinaryTree([10, 30, 15, 20, null, null, 5]);
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});
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it('Should converted binary tree to binary search tree', () => {
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const bTree = binaryTreeToBST(tree);
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expect(storeInorder(bTree)).toEqual([5, 10, 15, 20, 30]);
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});
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});
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/**
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* Given a Binary Tree, convert it to a Binary Search Tree.
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* The conversion must be done in such a way that keeps the original structure of Binary Tree.
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* Example 1
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Input:
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10
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/ \
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2 7
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/ \
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8 4
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Output:
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8
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/ \
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4 10
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/ \
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2 7
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*/
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const Node = require('../../_DataStructures_/Trees/BinaryTree/Node');
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// Helper function to store inorder traversal of a binary tree
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function storeInorder(root) {
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/** left - root - right */
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if (root === null) return [];
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// First store the left subtree
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let arr = [];
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const left = storeInorder(root.leftChild);
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arr = [...left, ...arr];
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// Append root's data
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arr = [...arr, root.value];
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// Store right subtree
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const right = storeInorder(root.rightChild);
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arr = [...arr, ...right];
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return arr;
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}
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// Helper function to copy elements from sorted array to make BST while keeping same structure
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// Runtime complexity iof this function is O(n) where n is number of nodes, as we are each node of tree one time.
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function arrayToBST(arr, root) {
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const node = root;
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// Base case
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if (!node) return null;
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const bstNode = new Node();
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// First update the left subtree
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const leftChild = arrayToBST(arr, node.leftChild);
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if (leftChild) {
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bstNode.leftChild = leftChild;
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}
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// update the root's data and remove it from sorted array
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// eslint-disable-next-line no-param-reassign
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bstNode.value = arr.shift();
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// Finally update the right subtree
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const rightChild = arrayToBST(arr, node.rightChild);
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if (rightChild) {
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bstNode.rightChild = rightChild;
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}
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return bstNode;
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}
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function binaryTreeToBST(bTree) {
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// Tree is empty
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if (!bTree.root) return null;
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const arr = bTree.preOrder();
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arr.sort((a, b) => a - b);
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const bst = arrayToBST(arr, bTree.root);
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return bst;
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}
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module.exports = {
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binaryTreeToBST,
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storeInorder,
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};

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