jan-brennenstuhl-HwtWJ5LraB8-unsplash.jpg

官方题解(这题我不会)

  1. /**
  2.  * Definition for a binary tree node.
  3.  * function TreeNode(val, left, right) {
  4.  *     this.val = (val===undefined ? 0 : val)
  5.  *     this.left = (left===undefined ? null : left)
  6.  *     this.right = (right===undefined ? null : right)
  7.  * }
  8.  */
  9. /**
  10.  * @param {TreeNode} root
  11.  * @return {number[][]}
  12.  */
  13. var levelOrder = function (root) {
  14.   const ret = [];
  15.   if (!root) {
  16.     return ret;
  17.   }
  19.   const q = [];
  20.   q.push(root);
  21.   while (q.length !== 0) {
  22.     const currentLevelSize = q.length;
  23.     ret.push([]);
  24.     for (let i = 1; i <= currentLevelSize; ++i) {
  25.       const node = q.shift();
  26.       ret[ret.length - 1].push(node.val);
  27.       if (node.left) q.push(node.left);
  28.       if (node.right) q.push(node.right);
  29.     }
  30.   }
  32.   return ret;
  33. };

解题思路(队列queue，广度优先搜索DFS)

使用队列先入先出的特性，依次填入根节点、左子树、右子树，之后再依次抛出即可。``