Print cousins of given node in a binary tree

Given a binary tree, print all cousins of a given node. Two nodes of binary tree are cousins of each other only if they have different parents but they have same level.


For example, consider below tree

level order traversal

6, 7 are cousins of node 4 or 5
4, 5 are cousins of node 6 or 7



The idea is to find level of given node in binary tree by doing a pre-order traversal of the tree. Once the level is found, we print all nodes present in that level which is not sibling of given node or the node itself.

C++ implementation –

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The time complexity of above solution is O(n) and need O(h) extra space for the call stack where h is the height of the tree.

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Vikky Agrawal
Vikky Agrawal

Java implementation: