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70 lines
941 B
Markdown
70 lines
941 B
Markdown
# [107. Binary Tree Level Order Traversal II](https://leetcode.com/problems/binary-tree-level-order-traversal-ii/)
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## 题目
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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).
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**For Example**:
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Given binary tree [3,9,20,null,null,15,7],
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```
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3
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/ \
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9 20
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/ \
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15 7
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```
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return its bottom-up level order traversal as:
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```
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[
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[15,7],
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[9,20],
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[3]
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]
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```
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## 题目大意
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按层序从下到上遍历一颗树。
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## 解题思路
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用一个队列即可实现。
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## 代码
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```go
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package leetcode
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/**
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* Definition for a binary tree node.
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* type TreeNode struct {
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* Val int
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* Left *TreeNode
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* Right *TreeNode
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* }
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*/
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func levelOrderBottom(root *TreeNode) [][]int {
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tmp := levelOrder(root)
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res := [][]int{}
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for i := len(tmp) - 1; i >= 0; i-- {
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res = append(res, tmp[i])
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}
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return res
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}
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``` |