// LeetCode template: function TreeNode(val) { this.val = val; this.left = this.right = null; } // Tool to convert array input to a tree: function fromList(values) { if (!values) return; let it = (function* () { for (let value of values) { yield value == null ? null : new TreeNode(value); } while (true) yield null; })(); let root = it.next().value; let nextlevel = [root]; while (nextlevel.length) { let level = nextlevel; nextlevel = []; for (let node of level) { if (node) { node.left = it.next().value; node.right = it.next().value; nextlevel.push(node.left, node.right); } } } return root; } // Your function var lowestCommonAncestor = function(root, p, q) { // return the path to the node let path = [] const search = (node, target) => { if (node === null) return false; path.push(node); if (node.val === target) return true; const leftSearched = search(node.left, target); if (leftSearched) return true; const rightSearched = search(node.right,target); if (rightSearched) return true; path.pop(); } search(root, p); const pathP = path; path = []; search(root, q); const pathQ = path; let result; while(pathP.length > 0 && pathQ.length > 0 && pathP[0] === pathQ[0]) { result = pathP[0]; pathP.shift(); pathQ.shift(); } return result; }; // Running your solution on some input let input = [3,5,1,6,2,0,8,null,null,7,4]; // Make the conversion that LeetCode would do let root = fromList(input); let lca = lowestCommonAncestor(root,5,1); // For your own purposes, just print the value of that node: console.log(lca.val); // 3