Find Bottom Left Tree Value

import { TreeNode } from '@algorithm/lib';
 
export function findBottomLeftValue(root: TreeNode | null): number {
  if (!root) {
    return -1;
  }
 
  let answer = root.val;
  const queue: TreeNode[] = [root];
  while (0 < queue.length) {
    const node = queue.shift()!;
    answer = node.val;
    if (node.right) {
      queue.push(node.right);
    }
    if (node.left) {
      queue.push(node.left);
    }
  }
 
  return answer;
}