Check if two linked lists merge. If so, where?

Question

This question may be old, but I couldn\'t think of an answer.

Say, there are two lists of different lengths, merging at a point; how do we know wher

Answer 1

Well, if you know that they will merge:

Say you start with:

A-->B-->C
        |
        V
1-->2-->3-->4-->5

1) Go through the first list setting each next pointer to NULL.

Now you have:

A   B   C

1-->2-->3   4   5

2) Now go through the second list and wait until you see a NULL, that is your merge point.

If you can't be sure that they merge you can use a sentinel value for the pointer value, but that isn't as elegant.