7 Data Structures for Problem Solving Free Online FlashCards

What is a string?

A string is an ordered sequence of characters used to represent text. It supports operations such as indexing, slicing, searching, concatenation, and replacement.

What does `word[0:4]` select?

The ending position is excluded, so `word[0:4]` selects positions 0, 1, 2, and 3.

What does string immutability mean?

Strings are commonly immutable: an apparent modification creates a new string instead of changing the original string in place.

How can repeated string construction be made more efficient?

Use a list to collect pieces and call `str.join()` once. This is often more efficient than repeatedly concatenating large strings.

What characterizes a Python list?

A list is an ordered, mutable collection whose elements can be accessed by position and whose size can often change during execution.

What is a record?

A record groups related fields describing one entity, with meaningful field names such as `id`, `name`, and `grade`.

What rule governs dictionary keys and updates?

A dictionary maps keys to values. Its keys must be unique, and assigning to an existing key replaces that key’s previous value.

How are rows, columns, and cells defined in a table?

In a table, each row is a record, each column is a field or attribute, and each cell is the value at a row-column intersection.

Which SQL operations match common collection changes?

`INSERT` stores a new record, `SELECT` accesses or searches records, `UPDATE` modifies records, and `DELETE` removes records.

Why combine collection types in nested structures?

A nested collection mirrors layered data: an outer list can contain student records, and each record can contain a name string and a scores list.

What should primarily guide data-structure selection?

Choose a data structure by identifying the operations the algorithm performs most often, such as positional access, lookup by label, ordering, or persistence.

What indexes are valid for a sequence of length $n$?

For a sequence of length $n$, the usual valid indexes are 0 through $n-1$. Thus, a three-element list has final valid index 2.