前序遍历: /*** Definition for a binary tree node.* public class TreeNode {* int val;* TreeNode left;* TreeNode right;* TreeNode(int x) { val = x; }* }*/
class Solution {public List<Integer> preorderTraversal(TreeNode root) {List<Intege
题目描述: Given a binary tree, return thelevel ordertraversal of its nodes' values. (ie, from left to right, level by level). For example: Given binary tree{3,9,20,#,#,15,7}, 3/ \9 20/ \15 7 return its level order traversal as: [[3],[9,20],[15