have more black nodesviolating rule or it must have two adjacent red nodesviolating rule convince yourself that this is true by experimenting with the applet null children remember that rule specifies all paths that go from the root to any leaf or to any null children must have the same number of black nodes null child is child that non-leaf node might havebut doesn' (that isa missing left child if the node has right childor vice versa thusin figure the path from to to the right child of (its null childhas only one black nodewhich is not the same as the paths to and which have two this arrangement violates rule although both paths to leaf nodes have the same number of black nodes black height is null child of black height is null child of black height is black height is figure path to null child the term black height is used to describe the number of black nodes from the root to given node in figure the black height of is of is still of is and so on rotations to balance treeyou need to physically rearrange the nodes if all the nodes are on the left of the rootfor exampleyou need to move some of them over to the right side this is done using rotations in this section we'll learn what rotations are and how to execute them rotations must do two things at once