107. Binary Tree Level Order Traversal II
Given a binary tree, return the bottom-up level order traversal of its nodes‘ values. (ie, from left to right, level by level from leaf to root).
For example:
Given binary tree [3,9,20,null,null,15,7],
3
/ 9 20
/ 15 7
return its bottom-up level order traversal as:
[ [15,7], [9,20], [3] ]
题意：层序遍历二叉树的变形，倒着输出二维数组的每一层节点值
代码如下：
/** * Definition for a binary tree node. * function TreeNode(val) { * this.val = val; * this.left = this.right = null; * } */ /** * @param {TreeNode} root * @return {number[][]} */ var levelOrderBottom = function(root) { let res=[]; if(!root) return res; let q=[]; q.push(root); let stack=[]; while(q.length>0){ let count=0; let size=q.length; let curr=[]; while(count<size){ let currNode=q.shift(); curr.push(currNode.val); if(currNode.left) q.push(currNode.left); if(currNode.right) q.push(currNode.right); count++; } stack.push(curr) } while(stack.length>0){ res.push(stack.pop()); } return res; };
107. Binary Tree Level Order Traversal II（js）
原文：https://www.cnblogs.com/xingguozhiming/p/10713153.html