|
| 1 | + |
| 2 | +>仰望星空的人,不应该被嘲笑 |
| 3 | + |
| 4 | +## 题目描述 |
| 5 | +给你一个二叉树,请你返回其按 **层序遍历** 得到的节点值。 (即逐层地,从左到右访问所有节点)。 |
| 6 | + |
| 7 | + |
| 8 | + |
| 9 | +示例: |
| 10 | + |
| 11 | +```javascript |
| 12 | +二叉树:[3,9,20,null,null,15,7], |
| 13 | + |
| 14 | + 3 |
| 15 | + / \ |
| 16 | + 9 20 |
| 17 | + / \ |
| 18 | + 15 7 |
| 19 | +``` |
| 20 | + |
| 21 | +返回其层次遍历结果: |
| 22 | + |
| 23 | +```javascript |
| 24 | +[ |
| 25 | + [3], |
| 26 | + [9,20], |
| 27 | + [15,7] |
| 28 | +] |
| 29 | +``` |
| 30 | + |
| 31 | +来源:力扣(LeetCode) |
| 32 | +链接:https://leetcode-cn.com/problems/binary-tree-level-order-traversal |
| 33 | +著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。 |
| 34 | + |
| 35 | + |
| 36 | +## 解题思路 |
| 37 | +直接用 `BFS`,对于每一层初始化空数组,然后存放每一层的节点值,然后迭代即可。 |
| 38 | + |
| 39 | +```javascript |
| 40 | +/** |
| 41 | + * Definition for a binary tree node. |
| 42 | + * function TreeNode(val) { |
| 43 | + * this.val = val; |
| 44 | + * this.left = this.right = null; |
| 45 | + * } |
| 46 | + */ |
| 47 | +/** |
| 48 | + * @param {TreeNode} root |
| 49 | + * @return {number[][]} |
| 50 | + */ |
| 51 | +var levelOrder = function (root) { |
| 52 | + if(!root) return []; |
| 53 | + let res = []; |
| 54 | + let queue = [root]; |
| 55 | + let cnt = 0; |
| 56 | + while (queue.length) { |
| 57 | + let size = queue.length; |
| 58 | + // 每一层初始化一个空数组 |
| 59 | + res.push([]); |
| 60 | + while (size--) { |
| 61 | + let node = queue.shift(); |
| 62 | + // 每一层的节点都存着 |
| 63 | + res[cnt].push(node.val); |
| 64 | + node.left && queue.push(node.left); |
| 65 | + node.right && queue.push(node.right); |
| 66 | + } |
| 67 | + // 迭代层次 |
| 68 | + ++cnt; |
| 69 | + } |
| 70 | + return res; |
| 71 | +}; |
| 72 | +``` |
| 73 | + |
| 74 | +## 最后 |
| 75 | +文章产出不易,还望各位小伙伴们支持一波! |
| 76 | + |
| 77 | +往期精选: |
| 78 | + |
| 79 | +<a href="https://github.com/Chocolate1999/Front-end-learning-to-organize-notes">小狮子前端の笔记仓库</a> |
| 80 | + |
| 81 | +<a href="https://github.com/Chocolate1999/leetcode-javascript">leetcode-javascript:LeetCode 力扣的 JavaScript 解题仓库,前端刷题路线(思维导图)</a> |
| 82 | + |
| 83 | +小伙伴们可以在Issues中提交自己的解题代码,🤝 欢迎Contributing,可打卡刷题,Give a ⭐️ if this project helped you! |
| 84 | + |
| 85 | + |
| 86 | +<a href="https://yangchaoyi.vip/">访问超逸の博客</a>,方便小伙伴阅读玩耍~ |
| 87 | + |
| 88 | + |
| 89 | + |
| 90 | +```javascript |
| 91 | +学如逆水行舟,不进则退 |
| 92 | +``` |
| 93 | + |
| 94 | + |
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