Please help me with this

#1

How to approach this problem

#2

@aryan hey, you can use trie here, what you can do is for all nodes of the trie , we calculate number of strings in the substree and then just apply combinatorics such -
NC2(total nodes in the subtree of current nodes)-summation of NC2(children in each nodes)

#3

After finding the strings for each node’s subtree. After that what to do, can you please explain it again

#4

@aryan hey bro that you have to apply P and c logic
just dry run this code you will get it bro

#5

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