Right rotation refers to the following: * In an

array An array is a systematic arrangement of similar objects, usually in rows and columns. Things called an array include: {{TOC right Music * In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...

, moving all items to the next higher location. The last item is moved to the first location, which has been vacated. * In a

list A ''list'' is any set of items in a row. List or lists may also refer to: People * List (surname) Organizations * List College, an undergraduate division of the Jewish Theological Seminary of America * SC Germania List, German rugby uni ...

, removing the

tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals ...

and inserting it at the

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may no ...

. * In

machine code In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a ver ...

(and assembly language) moving all bits in a register to the right, with the rightmost (

least significant bit In computing, bit numbering is the convention used to identify the bit positions in a binary number. Bit significance and indexing In computing, the least significant bit (LSB) is the bit position in a binary integer representing the binary ...

) becoming the leftmost.

Tree rotation

In a

binary search tree In computer science, a binary search tree (BST), also called an ordered or sorted binary tree, is a rooted binary tree data structure with the key of each internal node being greater than all the keys in the respective node's left subtree and ...

, a right rotation is the movement of a node, X, down to the right. This rotation assumes that X has a left child (or subtree). X's left child, R, becomes X's parent node and R's right child becomes X's new left child. This rotation is done to balance the tree; specifically when the left subtree of node X has a significantly (depending on the type of tree) greater height than its right subtree. Right rotations (and left) are ''order preserving'' in a

; it preserves the binary search tree property (an

in-order traversal In computer science, tree traversal (also known as tree search and walking the tree) is a form of graph traversal and refers to the process of visiting (e.g. retrieving, updating, or deleting) each node in a tree data structure, exactly once. ...

of the tree will yield the keys of the nodes in proper order).

AVL tree In computer science, an AVL tree (named after inventors Adelson-Velsky and Landis) is a self-balancing binary search tree. It was the first such data structure to be invented. In an AVL tree, the heights of the two child subtrees of any node ...

s and

red–black tree In computer science, a red–black tree is a kind of self-balancing binary search tree. Each node stores an extra bit representing "color" ("red" or "black"), used to ensure that the tree remains balanced during insertions and deletions. When the ...

s are two examples of binary search trees that use a right rotation. A single right rotation is done in O(1) time but is often integrated within the node insertion and deletion of

binary search trees In computer science, a binary search tree (BST), also called an ordered or sorted binary tree, is a rooted binary tree data structure with the key of each internal node being greater than all the keys in the respective node's left subtree and ...

. The rotations are done to keep the cost of other methods and tree height at a minimum.

References

Thomas H. Cormen Thomas H. Cormen is the co-author of ''Introduction to Algorithms'', along with Charles Leiserson, Ron Rivest, and Cliff Stein. In 2013, he published a new book titled '' Algorithms Unlocked''. He is a professor of computer science at Dartmout ...

Charles E. Leiserson Charles Eric Leiserson is a computer scientist, specializing in the theory of parallel computing and distributed computing, and particularly practical applications thereof. As part of this effort, he developed the Cilk multithreaded language. ...

, Ronald L. Rivest, and

Clifford Stein Clifford Seth Stein (born December 14, 1965), a computer scientist, is a professor of industrial engineering and operations research at Columbia University in New York, NY, where he also holds an appointment in the Department of Computer Scien ...

, 16 July 2001, ''Introduction to Algorithms'', second edition. McGraw-Hill, . Chapter 13. {{Use dmy dates, date=July 2019 Trees (data structures)