Lowest Common Ancestor in a Binary Tree

LowestCommonAncestorInABinaryTree.js

// https://www.geeksforgeeks.org/lowest-common-ancestor-binary-tree-set-1/

class Node {
  constructor(val, left, right) {
    this.val = val;
    this.left = left;
    this.right = right;
  };
}

function getLCA(root, n1, n2) {
  // The condition of finishing recursive:
  // 1. When node is null.
  // 2. When node is same as n1 or n2.
  if (!root) return null;
  if (root.val === n1 || root.val === n2) {
    return root;
  }
  const left = getLCA(root.left, n1, n2);
  const right = getLCA(root.right, n1, n2);
  if (left && right) {
    // 3. When left and right are both defined, return the ancestor.
    return root;
  }
  // 4. If one of them is defined, return the one that we found
  return left ? left : right;
}

const root = new Node(1);
root.left = new Node(2);
root.right = new Node(3);
root.left.left = new Node(4);
root.left.right = new Node(5);
root.right.left = new Node(6);
root.right.right = new Node(7);
const res = [[4,5], [4,6], [3,4], [2,4]].map((params) => getLCA(root, ...params).val).join(',');
console.log(res === '2,1,1,2');

// https://practice.geeksforgeeks.org/problems/lowest-common-ancestor-in-a-binary-tree/1
const example1 = new Node(1);
example1.left = new Node(2);
example1.right = new Node(3);
const example1Res = [[2,3]].map((params) => getLCA(example1, ...params).val).join(',');
console.log(example1Res === '1');

const example2 = new Node(5);
example2.left = new Node(2);
example2.left.left = new Node(3);
example2.left.right = new Node(4);
const example2Res = [[3,4]].map((params) => getLCA(example2, ...params).val).join(',');
console.log(example2Res === '2');