Vivek and Birthday Celebration getting segmentation fault in the code written by me

This is my code and i guess the logic is correct as i made a directed graph and applied dfs in it and count the minimum legth of the graph in it .

Algorithm ->
-> For each pair p(a,b), we add a connection from a to b i.e. we insert ‘b’ to the node[a]. Thus if ‘a’ is selected ‘b’ would automatically be selected.
-> Now we take each node[i] and traverse through the connections till all the leaf nodes and count the total nodes directly/indirectly connected to that particular node[i].
We find that node[i] which has the minimum number of connections.

Refer this for better understanding -:

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