The length and depth of a generalized table and the footer operation of the table head

Generalized table definitions

Generalized table (Lists, aka list) is a kind of nonlinear data structure, and it is a generalization of linear table. The generalized table relaxes the atomic limits on the table elements, allowing them to have their own structure. It is widely used in the field of artificial intelligence and other fields of table processing language in Lisp language. In Lisp language, generalized table is one of the most basic data structures, even the program of Lisp language is expressed as a series of generalized tables.

A generalized table is a finite sequence of A1,a2,...,ai,...,an of N (n≥0) elements.

which

①ai--is either an atom or a generalized table.

② generalized tables are usually written as: ls= (A1,a2,...,ai,...,an).

③ls is the name of the generalized table, and n is its length.

④ If the AI is a generalized table, it is called the sub-table of LS.

Attention:

① generalized tables are usually enclosed in parentheses, separating the elements with commas.

② in order to distinguish between atoms and generalized tables, write with uppercase letters representing generalized tables, with lowercase letters representing atoms.

③ if the generalized table LS is non-null (n≥1), then Al is the table header of LS, and the remaining elements of the table (A1,a2,...,an) are called the footer of LS.

④ Generalized tables are recursive-defined

I. Generalized table characteristics:
1. Hierarchy: The element of the generalized table can be a child table, and the element of the child table can be a child table, thus, the generalized table is a multi-level structure;
2. Sharing: Generalized tables can be shared by other tables.
3. Recursive table: A generalized table can be a sub-table of its own.

Second, depth and length

The Generalized table ((A, B, (), c), D), E, ((f), G)) is the length of ____, and the depth is ____.

The generalized table length is the number of commas in the first layer of parentheses to see that only one element is ((A, B, (), c), D), E, ((f), G), so the length is 1, the depth is the number of parentheses, and the depth is 4.


Third, the table head and the footer

According to the definition of table header and footer, the header of any non-null generalized table is the first element in a table, which can be an atom or a child table, and its footer must be a child table. That is, the head operation of the generalized table, what is the element taken out, and what is the result. However, the tail operation takes out an element that must be added to a table-"()" Problem: Known generalized table ls= ((a,b,c), (d,e,f)), the use of head and tail function to remove LS Zhongyuan sub-e operation is.
Known generalized table ls= ((a,b,c), (d,e,f)) therefore: tail (ls) = ((D,e,f)) head (tail (ls)) = (d,e,f) tail (head (tail (ls))) = (e,f) head (t AIL (Head (tail (LS))) =e