题目描述：
示例：
解法：

题目描述：

给定一个二叉树，返回其节点值自底向上的层次遍历。（即按从叶子节点所在层到根节点所在的层，逐层从左向右遍历）

示例：

给定二叉树 [3,9,20,null,null,15,7],

        3/ \9  20/  \15   7

返回其自底向上的层次遍历为：

    [[15,7],[9,20],[3]]

解法：

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     TreeNode *left;*     TreeNode *right;*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}* };*/
class Solution {
public:vector<vector<int>> levelOrderBottom(TreeNode* root) {vector<vector<int>> res;if(root){vector<int> level;vector<TreeNode*> cur;cur.push_back(root);vector<TreeNode*> nxt;while(!cur.empty()){nxt.clear();level.clear();for(TreeNode* node : cur){level.push_back(node->val);if(node->left){nxt.push_back(node->left);}if(node->right){nxt.push_back(node->right);}}res.push_back(level);cur = nxt;}}res = vector<vector<int>>(res.rbegin(), res.rend());return res;}
};

转载于:https://www.cnblogs.com/zhanzq/p/10557105.html

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leetcode 二叉树的层次遍历 II(Binary Tree Level Order Traversal II)

题目描述：

示例：

解法：

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