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‎Problemset/0958-Check Completeness of a Binary Tree/README.md

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# 958. Check Completeness of a Binary Tree
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Given the `root` of a binary tree, determine if it is a *complete binary tree*.
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In a [**complete binary**](http://en.wikipedia.org/wiki/Binary_tree#Types_of_binary_trees) tree, every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between `1` and <code>2<sup>h</sup></code> nodes inclusive at the last level `h`.
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#### Example 1:
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![](https://assets.leetcode.com/uploads/2018/12/15/complete-binary-tree-1.png)
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<pre>
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<strong>Input:</strong> root = [1,2,3,4,5,6]
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<strong>Output:</strong> true
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<strong>Explanation:</strong> Every level before the last is full (ie. levels with node-values {1} and {2, 3}), and all nodes in the last level ({4, 5, 6}) are as far left as possible.
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</pre>
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#### Example 2:
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![](https://assets.leetcode.com/uploads/2018/12/15/complete-binary-tree-2.png)
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<pre>
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<strong>Input:</strong> root = [1,2,3,4,5,null,7]
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<strong>Output:</strong> false
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<strong>Explanation:</strong> The node with value 7 isn't as far left as possible.
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</pre>
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#### Constraints:
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* The number of nodes in the tree is in the range `[1, 100]`.
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* `1 <= Node.val <= 1000`
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## Solutions (Python)
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### 1. Solution
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```Python
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def isCompleteTree(self, root: Optional[TreeNode]) -> bool:
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nodes = [root]
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depth = 0
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while True:
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children = []
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if nodes[0] == None:
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return True
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if len(nodes) != 2 ** depth:
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return False
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for node in nodes:
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if node is not None:
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children.append(node.left)
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children.append(node.right)
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for i in range(1, len(children)):
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if children[i - 1] is None and children[i] is not None:
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return False
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nodes = children
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depth += 1
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```

‎Problemset/0958-Check Completeness of a Binary Tree/README_CN.md

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# 958. 二叉树的完全性检验
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给你一棵二叉树的根节点 `root` ，请你判断这棵树是否是一棵 **完全二叉树** 。
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在一棵 [**完全二叉树**](https://baike.baidu.com/item/%E5%AE%8C%E5%85%A8%E4%BA%8C%E5%8F%89%E6%A0%91/7773232?fr=aladdin) 中，除了最后一层外，所有层都被完全填满，并且最后一层中的所有节点都尽可能靠左。最后一层（第 `h` 层）中可以包含 `1` 到 <code>2<sup>h</sup></code> 个节点。
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#### 示例 1:
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![](https://assets.leetcode.com/uploads/2018/12/15/complete-binary-tree-1.png)
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<pre>
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<strong>输入:</strong> root = [1,2,3,4,5,6]
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<strong>输出:</strong> true
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<strong>解释:</strong> 最后一层前的每一层都是满的（即，节点值为 {1} 和 {2,3} 的两层），且最后一层中的所有节点（{4,5,6}）尽可能靠左。
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</pre>
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#### 示例 2:
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![](https://assets.leetcode.com/uploads/2018/12/15/complete-binary-tree-2.png)
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<pre>
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<strong>输入:</strong> root = [1,2,3,4,5,null,7]
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<strong>输出:</strong> false
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<strong>解释:</strong> 值为 7 的节点不满足条件「节点尽可能靠左」。
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</pre>
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#### 提示:
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* 树中节点数目在范围 `[1, 100]` 内
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* `1 <= Node.val <= 1000`
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## 题解 (Python)
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### 1. 题解
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```Python
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def isCompleteTree(self, root: Optional[TreeNode]) -> bool:
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nodes = [root]
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depth = 0
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while True:
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children = []
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if nodes[0] == None:
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return True
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if len(nodes) != 2 ** depth:
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return False
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for node in nodes:
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if node is not None:
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children.append(node.left)
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children.append(node.right)
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for i in range(1, len(children)):
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if children[i - 1] is None and children[i] is not None:
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return False
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nodes = children
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depth += 1
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```

‎Problemset/0958-Check Completeness of a Binary Tree/Solution.py

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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def isCompleteTree(self, root: Optional[TreeNode]) -> bool:
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nodes = [root]
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depth = 0
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while True:
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children = []
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if nodes[0] == None:
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return True
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if len(nodes) != 2 ** depth:
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return False
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for node in nodes:
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if node is not None:
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children.append(node.left)
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children.append(node.right)
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for i in range(1, len(children)):
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if children[i - 1] is None and children[i] is not None:
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return False
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nodes = children
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depth += 1

‎README.md

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[953][953l] |[Verifying an Alien Dictionary][953] |![py]
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[954][954l] |[Array of Doubled Pairs][954] |![py]
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[957][957l] |[Prison Cells After N Days][957] |![rs]
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[958][958l] |[Check Completeness of a Binary Tree][958] |![py]
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[961][961l] |[N-Repeated Element in Size 2N Array][961] |![rs]
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[962][962l] |[Maximum Width Ramp][962] |![rs]
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[965][965l] |[Univalued Binary Tree][965] |![py]
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[953]:Problemset/0953-Verifying%20an%20Alien%20Dictionary/README.md#953-verifying-an-alien-dictionary
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[954]:Problemset/0954-Array%20of%20Doubled%20Pairs/README.md#954-array-of-doubled-pairs
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[957]:Problemset/0957-Prison%20Cells%20After%20N%20Days/README.md#957-prison-cells-after-n-days
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[958]:Problemset/0958-Check%20Completeness%20of%20a%20Binary%20Tree/README.md#958-check-completeness-of-a-binary-tree
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[961]:Problemset/0961-N-Repeated%20Element%20in%20Size%202N%20Array/README.md#961-n-repeated-element-in-size-2n-array
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[962]:Problemset/0962-Maximum%20Width%20Ramp/README.md#962-maximum-width-ramp
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[965]:Problemset/0965-Univalued%20Binary%20Tree/README.md#965-univalued-binary-tree
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[953l]:https://leetcode.com/problems/verifying-an-alien-dictionary/
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[954l]:https://leetcode.com/problems/array-of-doubled-pairs/
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[957l]:https://leetcode.com/problems/prison-cells-after-n-days/
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[958l]:https://leetcode.com/problems/check-completeness-of-a-binary-tree/
31903193
[961l]:https://leetcode.com/problems/n-repeated-element-in-size-2n-array/
31913194
[962l]:https://leetcode.com/problems/maximum-width-ramp/
31923195
[965l]:https://leetcode.com/problems/univalued-binary-tree/

‎README_CN.md

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[953][953l] |[验证外星语词典][953] |![py]
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[954][954l] |[二倍数对数组][954] |![py]
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[957][957l] |[N 天后的牢房][957] |![rs]
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[958][958l] |[二叉树的完全性检验][958] |![py]
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[961][961l] |[重复 N 次的元素][961] |![rs]
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[962][962l] |[最大宽度坡][962] |![rs]
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[965][965l] |[单值二叉树][965] |![py]
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[953]:Problemset/0953-Verifying%20an%20Alien%20Dictionary/README_CN.md#953-验证外星语词典
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[954]:Problemset/0954-Array%20of%20Doubled%20Pairs/README_CN.md#954-二倍数对数组
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[957]:Problemset/0957-Prison%20Cells%20After%20N%20Days/README_CN.md#957-n-天后的牢房
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[958]:Problemset/0958-Check%20Completeness%20of%20a%20Binary%20Tree/README_CN.md#958-二叉树的完全性检验
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[961]:Problemset/0961-N-Repeated%20Element%20in%20Size%202N%20Array/README_CN.md#961-重复-n-次的元素
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[962]:Problemset/0962-Maximum%20Width%20Ramp/README_CN.md#962-最大宽度坡
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[965]:Problemset/0965-Univalued%20Binary%20Tree/README_CN.md#965-单值二叉树
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[953l]:https://leetcode.cn/problems/verifying-an-alien-dictionary/
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[954l]:https://leetcode.cn/problems/array-of-doubled-pairs/
31893191
[957l]:https://leetcode.cn/problems/prison-cells-after-n-days/
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[958l]:https://leetcode.cn/problems/check-completeness-of-a-binary-tree/
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[961l]:https://leetcode.cn/problems/n-repeated-element-in-size-2n-array/
31913194
[962l]:https://leetcode.cn/problems/maximum-width-ramp/
31923195
[965l]:https://leetcode.cn/problems/univalued-binary-tree/

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