LeetCode-199. Binary Tree Right Side View

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问题描述

Given the root of a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.

Example :

img

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Input: root = [1,2,3,null,5,null,4]
Output: [1,3,4]

Constraints:

  • The number of nodes in the tree is in the range [0, 100].
  • -100 <= Node.val <= 100

解答

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/*
 * @Description: 199. Binary Tree Right Side View
 * @Author: libk
 * @Github: https://github.com/libk
 */
/**
 * 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[]}
 */
const rightSideView = function (root) {
  if (!root) {
    return []
  }
  const queue = [root]
  const res = []

  while (queue.length) {
    let curLength = queue.length
    let cur = null
    while (curLength--) {
      cur = queue.shift()
      if (cur.left) {
        queue.push(cur.left)
      }
      if (cur.right) {
        queue.push(cur.right)
      }
    }
    res.push(cur.val)
  }
  return res
}