LeetCode力扣 107. 二叉樹的層次遍歷 II Binary Tree Level Order Traversal II 題解代碼 JavaScript

問題 https://leetcode-cn.com/problems/binary-tree-level-order-traversal-ii/

練習使用JavaScript解答

/**
 * 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) {
    var arr = [[],], que = [];
    var a, level = root, levelt;
    if(!root)
        return [];
    que.push(root);
    while(que.length) {
        a = que.shift();
        arr[arr.length-1].push(a.val);
        if(a.left) {
            que.push(a.left);
            levelt = a.left;
        }
        if(a.right) {
            que.push(a.right);
            levelt = a.right;
        }
        if(level == a && que.length) {
            arr[arr.length] = [];
            level = levelt;
        }
    }
    return arr.reverse();
};