lowestCommonAncestor.js

// TC: O(h) SC: O(1)

function lowestCommonAncestor(root, p, q) {
    let currNode = root;

    while(currNode !== null) {
        if(currNode.value > p.value && currNode.value > q.value) {
            currNode = currNode.left;
        } else if(currNode.value < p.value && currNode.value < q.value) {
            currNode = currNode.right;
        } else {
            return currNode;
        }
    }
    return null;
}

class TreeNode {
    constructor(value) {
      this.left = null;
      this.right = null;
      this.value = value;
    }
}

let root1 = new TreeNode(5);
root1.left = new TreeNode(1);
root1.right = new TreeNode(8);
root1.left.left = new TreeNode(0);
root1.left.right = new TreeNode(2);
root1.right.left = new TreeNode(7);
root1.right.right = new TreeNode(9);

console.log(lowestCommonAncestor(root1, new TreeNode(0), new TreeNode(2)).value);
console.log(lowestCommonAncestor(root1, new TreeNode(8), new TreeNode(9)).value);