Data structure: The data structure is the mode of information. It is mainly used to reflect the internal configuration of a data, which is the components of a data, which is constituted in any configuration. The data structure is divided into logically data structures (reflecting logical relationships between component data) and physical data structures (reflecting the storage schedule of the component data). From the perspective of discipline, the data structure is a discipline of computer operation objects and the relationship between the computer and the relationship between the computer and the relationship between the procedures. Its research content is three aspects: the logical structure of the data; the physical storage structure of the data; the operation of the data (ie, the algorithm). The design of the general algorithm depends on the logical structure of the data, and the implementation of the algorithm depends on the physical storage structure of the data. A good data structure can improve the efficiency of the algorithm. Generally, a data structure corresponds to a set of algorithms, and the data structure is operated by this set of algorithms, referred to as the basic operation of the data structure (such as Establish, delete data structure, etc.). The study of data structures not only involves research on computer hardware, such as storage devices and access methods, but also to solve the problem of compilation principles, operating systems, database systems in memory of allocation issues in memory. Abstract Data Type ADT (Abstract Data Type): Abbreviation data type, both a mathematical model and a set of operations defined on the model, because it implements the hidden and localization of information, providing a definition The interface provides an abstract data implementation and concealed processing on the data structure, which looks all the basic operations of the data structure and the data structure as a whole (module model), the logical structure of the data structure is represented as a private member, Basic operations are expressed as public methods. Therefore, it is independent of the physical structure, so that the software system is built on the data, similar to the concept of object-oriented language. Data: The data is a collection concept, and is the general name of objective symbols that can be entered into the computer and is processed by the computer. The data item is the minimum unit of data inseparable, the data item constitutes a data element; the data element is the basic unit of the data, which is "individual" in the data, also known as "record" or "expression"; the same properties of data elements Data objects; and data objects constitute data. The data structure is a collection of one or more data elements of a particular relationship. Data logical structure: 1. Collection (SETs): There is no other relationship in addition to the relationship between the data elements. 2. Linear (Lists): There is a one-to-one procedure of the data element. Features: Some and have only one element inadequate elements. There is only one element without a rear elements. There are only one of the remaining elements and there is only one forever and a successive element. 3. Tree (TREES): There is a pair of data elements. Features: Any element has a maximum of one, zero or more subsequent, is a typical nonlinear structure. 4. Graphs: There are many-to-many relationships in data elements. Features: Any element can have multiple orders or multiple successes, is a multi-to-many forward subsequent relationship. Tables and trees are the most commonly used two high-efficiency data structures, and many highly efficient algorithms can be implemented with both data structures. Table is a linear structure (full order relationship), number (predecessor or hierarchical relationship) and diagram (weak order or local ordered Weak / Local ORDERS) is a non-linear structure. The physical structure of the data structure is the representation of the logical structure (also known as storage image image). Four basic mappings: sequential, connection, indexed, hashing. Since data for each logical structure can be stored by four different physical structures, 4 * 4 may be stored. But not all possible combinations are reasonable. Any operation of the data structure must maintain the data structure for the original logic and physical structure when changing the domain of the data element (node) or node. How to judge the good and bad data structure: If a DS can be converted to a linear DS (such as a linear table) through some "linear rule", it is called a good DS. Good DS usually corresponds to a good (efficient) algorithm.
