Question

Recently, I have been going through search trees and I encountered red-black trees, the point confusing me is, In r-b tree, the root node should be black thats fine, now how will I decide whether the incoming node assumes red or black color.

I have gone through the wiki article but have not found a solution for this. I might be wrong, but I would be happy if someone can guide me through the exact material.

[Edit]
That is for example, if my keys are {7, 2, 4, 1, 9, 10, 8}

Here 7 is root and it assumes black color, but what color does 2 assume? How do we decide that? And how do we decide what color the other nodes assume?

                                  7 - (Black)
                   2                              9
           1                   4        8                    10
        NIL   NIL          NIL  NIL   NIL  NIL            NIL  NIL

Do we have a random toss that decides the color of the node to be red or black. Or is it some other process.

Thank you.

Answer 1

Look at the lecture about red-black trees on MIT open courseware.

http://ocw.mit.edu/OcwWeb/Electrical-Engineering-and-Computer-Science/6-046JFall-2005/VideoLectures/

I found them to be very helpful.

Now if I remember correctly, you always insert new node as black node and then proceed to the necessary corrections (repainting and/or rotations)