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Implement Binary Tree to Binary Search Tree Conversion - Solution #127
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,7 @@ | ||
| module.exports = class Node { | ||
| constructor(value) { | ||
| this.value = value; | ||
| this.leftChild = null; // will be a node | ||
| this.rightChild = null; // will be a node | ||
| } | ||
| }; | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,19 @@ | ||
| const { binaryTreeToBST, storeInorder } = require('.'); | ||
| const Node = require('./Node'); | ||
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| describe('Binary tree to binary search tree', () => { | ||
| let tree; | ||
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| describe('Create Binary Tree', () => { | ||
| tree = new Node(10); | ||
| tree.leftChild = new Node(30); | ||
| tree.leftChild.leftChild = new Node(20); | ||
| tree.rightChild = new Node(15); | ||
| tree.rightChild.rightChild = new Node(5); | ||
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| }); | ||
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| it('Should converted binary tree to binary search tree', () => { | ||
| binaryTreeToBST(tree); | ||
| expect(storeInorder(tree)).toEqual([5, 10, 15, 20, 30]); | ||
| }); | ||
| }); | ||
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,65 @@ | ||
| /** | ||
| * Given a Binary Tree, convert it to a Binary Search Tree. | ||
| * The conversion must be done in such a way that keeps the original structure of Binary Tree. | ||
| * Example 1 | ||
| Input: | ||
| 10 | ||
| / \ | ||
| 2 7 | ||
| / \ | ||
| 8 4 | ||
| Output: | ||
| 8 | ||
| / \ | ||
| 4 10 | ||
| / \ | ||
| 2 7 | ||
| */ | ||
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| // Helper function to store inorder traversal of a binary tree | ||
| function storeInorder(root) { | ||
| /** left - root - right */ | ||
| if (root === null) return []; | ||
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| // First store the left subtree | ||
| let arr = []; | ||
| const left = storeInorder(root.leftChild); | ||
| arr = [...left, ...arr]; | ||
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| // Append root's data | ||
| arr = [...arr, root.value]; | ||
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| // Store right subtree | ||
| const right = storeInorder(root.rightChild); | ||
| arr = [...arr, ...right]; | ||
| return arr; | ||
| } | ||
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I think a better way to do this is to create a file inside Problems/tree-traversal directory nd have the following:
And re-use the function here. Alternatively, I am going forward to create these as helpers inside DataStructures/Trees/traversal so that they can be re-used |
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| // Helper function to copy elements from sorted array to make BST while keeping same structure | ||
| function arrayToBST(arr, root) { | ||
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Can you mention the runtime complexity of this function? |
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| const node = root; | ||
| // Base case | ||
| if (!node) return; | ||
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| // First update the left subtree | ||
| arrayToBST(arr, node.leftChild); | ||
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| // update the root's data and remove it from sorted array | ||
| node.value = arr.shift(); | ||
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| // Finally update the right subtree | ||
| arrayToBST(arr, node.rightChild); | ||
| } | ||
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| function binaryTreeToBST(root) { | ||
| // Tree is empty | ||
| if (!root) return; | ||
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| const arr = storeInorder(root); | ||
| arr.sort((a, b) => a - b); | ||
| arrayToBST(arr, root); | ||
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| } | ||
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| module.exports = { | ||
| binaryTreeToBST, | ||
| storeInorder, | ||
| }; | ||