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Commit 1387eef

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amahdyTheSTL
authored andcommitted
LCA implementation (fixes knaxus#89) (knaxus#91)
* Create solution file * Move to correct folder * Add the algorithm Ref: https://www.geeksforgeeks.org/lowest-common-ancestor-in-a-binary-search-tree/ * Add a test case * Fix test case * Fix test by adding missing arguments * Move to inside BST folder * Move to inside BST folder * Add more tests and use BST class * Fix variable declaration * Update reference * Match naming used in BST
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/**
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* Lowest Common Ancestor in a Binary Search Tree.
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*
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* Given values of two values n1 and n2 in a Binary Search Tree, find the Lowest Common Ancestor (LCA). You may assume that both the values exist in the tree.
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*/
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function lca(node, n1, n2) {
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if (node == null)
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return null;
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// If both n1 and n2 are smaller than root, then LCA lies in left
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if (node.value > n1 && node.value > n2)
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return lca(node.leftChild, n1, n2);
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// If both n1 and n2 are greater than root, then LCA lies in right
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if (node.value < n1 && node.value < n2)
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return lca(node.rightChild, n1, n2);
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return node;
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}
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module.exports = {
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lca,
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};
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const { lca } = require('.');
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const BinarySearchTree = require('../index');
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// Quick JSON equivalent
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// {"left":{"left":{"data":4},"right":{"left":{"data":10},"right":{"data":14},"data":12},"data":8},"right":{"data":22},"data":20}
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describe('LCA', () => {
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let bst = new BinarySearchTree(20);
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bst.add(22);
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bst.add(8);
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bst.add(12);
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bst.add(4);
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bst.add(14);
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bst.add(10);
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it('Should return 12', () => {
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expect(lca(bst.root, 10, 14).value).toEqual(12);
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});
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it('Should return 8', () => {
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expect(lca(bst.root, 14, 8).value).toEqual(8);
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});
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it('Should return 20', () => {
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expect(lca(bst.root, 10, 22).value).toEqual(20);
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});
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});

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