Data Structure BASICS (19) and data structure basics 19

Data Structure BASICS (19) and data structure basics 19
Double Rotation

A single rotation problem sometimes occurs (as shown in ):

(If the child node [k1] on the inner side is too deep, moving it one way will not solve the problem)

 

So there is a double rotation.

Double rotation to the right:

1. First, take k1 as the axis, and k1 and k2 rotate to the left;

2. Take k3 as the axis, and k3 and k1 after rotation rotate to the right;

/// Implement // double rotate template to the right <typename Type> void RedBlackTree <Type>: doubleRotateWithLeftChild (Node * & k3) const {// first place its left son (k1) rotate rotateWithRightChild (k3-> left) to the left, and then rotate rotateWithLeftChild (k3) to the right );}

Rotate to the left:

1. First, use k3 as the axis, and k2 and k3 rotate to the right;

2. Take k1 as the axis, and k1 and k2 after rotation rotate to the left;

/// Implement // rotate the template <typename Type> void RedBlackTree <Type>: doubleRotateWithRightChild (Node * & k1) const {// first set its right son (k2) rotate rotateWithLeftChild (k1-> right) to the right, and then rotate rotateWithRightChild (k1) to the left.} // note: in fact, the red and black trees do not use double rotation, but implement a rotate operation by themselves. // here, we only want to learn the theory of double rotation;

Test (after dual rotation ):

(Construct a binary search tree. The left side is before rotation, the right side is after rotation, and the 8 side is used as the axis for double rotation)

Int main () {// use NEG_INF to represent negative infinity const int NEG_INF =-999999; RedBlackTree <int> tree (NEG_INF); // test data tree during double spin. insert (12); tree. insert (16); tree. insert (8); tree. insert (10); tree. insert (4); tree. insert (14); tree. insert (2); tree. insert (6); tree. insert (5); cout <tree. header-> right-> element <endl; // 12 cout <tree. header-> right-> left-> element <endl; // 8 cout <tree. header-> right-> element <endl; // 16 cout <tree. header-> right-> left-> element <endl; // 4 cout <tree. header-> right-> left-> right-> element <endl; // 10 cout <tree. header-> right-> left-> element <endl; // 14 // cout <tree. header-> right-> left-> element <endl; // 5 has been used as a sentinel // cout <tree. header-> right-> left-> right-> element <endl; // 5 cout <tree. header-> right-> left-> element <endl; // 2 cout <tree. header-> right-> left-> right-> element <endl; // 6 cout <tree. header-> right-> left-> element <endl; // 5 cout <"\ n "<endl; // rotate the tree to the right based on 8. doubleRotateWithLeftChild (tree. header-> right-> left); cout <tree. header-> right-> element <endl; // 12 cout <tree. header-> right-> left-> element <endl; // 6 cout <tree. header-> right-> element <endl; // 16 cout <tree. header-> right-> left-> element <endl; // 4 cout <tree. header-> right-> left-> right-> element <endl; // 8 cout <tree. header-> right-> left-> element <endl; // 14 cout <tree. header-> right-> left-> element <endl; // 2 cout <tree. header-> right-> left-> right-> element <endl; // 5 cout <tree. header-> right-> left-> right-> element <endl; // 10 return 0 ;}

Exception

// Exception construction used in the implementation of the Red/black tree: class DSException {public: DSException (const string & _ message = string (): message (_ message ){}~ DSException () {} virtual string what () const {return message;} virtual string toString () const {return "Exception:" + what ();} private: std :: string message ;}; class DuplicateItemException: public DSException {public: DuplicateItemException (const string & _ msg = string (): DSException (_ msg ){}};