On Wed, 2012-07-11 at 18:12 -0700, Michel Lespinasse wrote: > > In __rb_erase_color(), some of the cases are more complicated than you drew however, because some node colors aren't known. Right, the wikipedia article draws them blank, I couldn't come up with a 3rd case, although maybe we can annotate them like (P) to mean blank.. > This is what I ended up with: > > * 5), then the longest possible path due to 4 is 2B. > * > * We shall indicate color with case, where black nodes are uppercase and red > - * nodes will be lowercase. > + * nodes will be lowercase. Unknown color nodes shall be drawn as red with > + * some accompanying text comment. > */ > > + /* > + * Case 2 - sibling color flip > + * (p could be either color here) > + * > + * p p > + * / \ / \ > + * N S --> N s > + * / \ / \ > + * Sl Sr Sl Sr > + * > + * This leaves us violating 5), so > + * recurse at p. If p is red, the > + * recursion will just flip it to black > + * and exit. If coming from Case 1, > + * p is known to be red. > + */ > > + /* > + * Case 3 - right rotate at sibling > + * (p could be either color here) > + * > + * p p > + * / \ / \ > + * N S --> N Sl > + * / \ \ > + * sl Sr s > + * \ > + * Sr > + */ > > + /* > + * Case 4 - left rotate at parent + color flips > + * (p and sl could be either color here. > + * After rotation, p becomes black, s acquires > + * p's color, and sl keeps its color) > + * > + * p s > + * / \ / \ > + * N S --> P Sr > + * / \ / \ > + * sl sr N sl > + */ Yes, very nice.. someday when I'm bored I might expand the comments with the reason why we're doing the given operation. Also, I was sorely tempted to rename your tmp1,tmp2 variables to sl and sr. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href