/*
 * @lc app=leetcode.cn id=199 lang=javascript
 *
 * [199] 二叉树的右视图
 */

// @lc code=start
/**
 * 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) {
  if (!root) return []
  const result = [];
  const queue = [];
  queue.push(root);
  while (queue.length) {
    let len = queue.length;
    const curLevel = [];
    while (len > 0) {
      const node = queue.shift();
      curLevel.push(node.val);
      node.left && queue.push(node.left);
      node.right && queue.push(node.right);
      len--;
    }
    result.push(curLevel[curLevel.length - 1]);
  }
  return result;
};
// @lc code=end