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g2601_2700.s2641_cousins_in_binary_tree_ii.readme.md Maven / Gradle / Ivy

2641\. Cousins in Binary Tree II

Medium

Given the `root` of a binary tree, replace the value of each node in the tree with the **sum of all its cousins' values**.

Two nodes of a binary tree are **cousins** if they have the same depth with different parents.

Return _the_ `root` _of the modified tree_.

**Note** that the depth of a node is the number of edges in the path from the root node to it.

**Example 1:**

![](https://assets.leetcode.com/uploads/2023/01/11/example11.png)

**Input:** root = [5,4,9,1,10,null,7]

**Output:** [0,0,0,7,7,null,11]

**Explanation:** The diagram above shows the initial binary tree and the binary tree after changing the value of each node. 
- Node with value 5 does not have any cousins so its sum is 0. 
- Node with value 4 does not have any cousins so its sum is 0. 
- Node with value 9 does not have any cousins so its sum is 0. 
- Node with value 1 has a cousin with value 7 so its sum is 7. 
- Node with value 10 has a cousin with value 7 so its sum is 7. 
- Node with value 7 has cousins with values 1 and 10 so its sum is 11.

**Example 2:**

![](https://assets.leetcode.com/uploads/2023/01/11/diagram33.png)

**Input:** root = [3,1,2]

**Output:** [0,0,0]

**Explanation:** The diagram above shows the initial binary tree and the binary tree after changing the value of each node.
- Node with value 3 does not have any cousins so its sum is 0. 
- Node with value 1 does not have any cousins so its sum is 0. 
- Node with value 2 does not have any cousins so its sum is 0.

**Constraints:**

*   The number of nodes in the tree is in the range [1, 105].
*   1 <= Node.val <= 104