- Difficulty: Medium
- Tags: LeetCode, Medium, Tree, Depth-First Search, Breadth-First Search, Hash Table, Binary Tree, leetcode-2641, O(n), O(w), BFS
Problem
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:
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:
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