/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var rightSideView = function(root) {
    // simple case
    if (!root) return [];
    
    // set up queue for BFS
    let q = [];
    let result = [];
    q.push(root);
    
    // check each level and take the furthest right
    while (q.length > 0) {
        let nodes = q.length;
        result.push(q[0].val);
        for (let i = 0; i < nodes; i++) {
            let curNode = q.shift();
            if (curNode.right) {
                q.push(curNode.right);
            }
            if (curNode.left) {
                q.push(curNode.left);
            }
        }
    }
    return result;
};