Red-Black trees have introduced a new property in the binary search tree that means an extra property of color (red, black). However, as these trees grow, in their operations such as insertion, deletion, it becomes complexes to retain all the properties, especially in case of deletion. Therefore, a new type of binary search tree can be defined which has no property of having a color, however has a new property introduced depend on the color that is the information for the new. This information of the level of any node is stored into a small integer (might be 8 bits). Now, AA-trees are described in terms of level of each node rather than storing a color bit with each node. A red-black tree utilized to have several conditions to be satisfied regarding its color and AA-trees have also been designed in such a way that it msut satisfy certain conditions regarding its new property, i.e., level.
The level of a node will be as:
1. Same as its parent, if the node is red.
2. One if the node is a leaf.
3. Level will be one less than the level of its parent, if the color of node is black.
Any red-black tree can be changed into an AA-tree by translating its color structure to levels such that left child is always one level lower than its parent & right child is always similar or at one level lower than its parent. While the right child is at same level to its parent, then a horizontal link is established among them. Thus, we conclude that it is essential that horizontal links are always at the right side and that there might not be two consecutive links. Taking into concern of all the above properties, we illustrates AA-tree as follows
After having a look at the AA-tree above, now we look at different operations which can be performed at such trees.