Finding the intersecting node from two intersecting linked lists

Question

Suppose there are two singly linked lists both of which intersect at some point and become a single linked list.

The head or start pointers of both the lists are kno

Answer 1

This takes O(M+N) time and O(1) space, where M and N are the total length of the linked lists. Maybe inefficient if the common part is very long (i.e. M,N >> m,n)

1. Traverse the two linked list to find M and N.
2. Get back to the heads, then traverse |M − N| nodes on the longer list.
3. Now walk in lock step and compare the nodes until you found the common ones.

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Edit: See more here.