Defines the simplified vector class, which is extended by four elements.
This class is applicable to the C language development scenario where the data volume is small and dynamic expansion is required.
Compares the sizes of key1 and key2, which are provided by users. The value 1 indicates that key1 is greater than key2, the value 0 indicates that key1 is equal to key2, and the value -1 indicates that key1 is less than key2. The default value is NULL.
Data storage pointer
Number of data records that have been released. The initial value is 0.
Converts a data element into a key for comparison. The key is provided by users, and the default value is NULL.
Maximum number of data records that can be stored. The initial value is 0.
Peak value of the number of stored data records. The initial value is 0.