Question

Sort a list of strings by increasing length, and so that strings of the same length are sorted lexicographically.

Short answer

Sort by length first, then lexicographic order for ties: ['date', 'kiwi', 'apple', 'banana', 'cherry'].

Step-by-step solution

Understand the Problem

We need to sort a list of strings first by their length in increasing order, and then, for strings of equal length, sort them lexicographically (alphabetically).

Arrange Example Data

Consider an example list: ['banana', 'apple', 'kiwi', 'cherry', 'date']. The goal is to sort this list by increasing string length and then lexicographically for strings of the same length.

Initial Sort by Length

Sort the list by the length of each string. The sorted list will be ['kiwi', 'date', 'apple', 'banana', 'cherry'] since 'kiwi' and 'date' have the shortest lengths, followed by 'apple', 'banana', and 'cherry'.

Lexicographic Sort for Equal Lengths

Check for strings of equal length: 'kiwi' and 'date' are both 4 characters long. Sort these lexicographically to get ['date', 'kiwi']. Replace them in the list: ['date', 'kiwi', 'apple', 'banana', 'cherry'].

Finalize Sorted List

Ensure the final list respects both sorting conditions: ['date', 'kiwi', 'apple', 'banana', 'cherry'] is sorted by length first and by lexicographic order for strings of the same length.

Key concepts

Lexicographic Order

Lexicographic order is similar to the order found in dictionaries. This method of sorting arranges strings based on their alphabetical sequence. Each character is compared individually, starting from the first.
To determine which string comes first, compare the first character of each string. If they are the same, move to the next character and repeat this process until a difference is found.
For example, consider 'apple' and 'banana'. The strings are compared letter by letter until a difference is found at the first letter: 'a' comes before 'b', so 'apple' appears before 'banana'.
In cases where strings have the same series of characters, their lengths determine their order, i.e., shorter strings come first. This alphabetical order is essential when sorting strings of equal length, as it creates a consistent method of prioritizing one string over another.

String Manipulation

String manipulation involves the process of examining, altering, and applying operations to strings. These operations are critical in sorting tasks because they enable the necessary comparisons to occur.

• Finding the length of a string: Utilize functions like `len()` in Python to determine how many characters a string contains.
• Character comparison: Compare each character within two strings to see which one should precede the other lexicographically.
• Identify and extract specific substrings: Useful in cases where only part of the string is needed for a certain operation, like sorting or filtering.

Understanding these operations allows you to effectively manipulate strings for sorting and other tasks. They provide the foundational skills needed to handle textual data logically, often through comparison and restructuring methods.

List Sorting

List sorting is a fundamental computing task that involves arranging data in a predefined sequence, often numerical or lexicographical. Sorting lists of strings requires understanding both the criteria and mechanisms of sorting.

• Sorting by Length: Use algorithms that can sort based on the integer result from measuring string lengths.
• Secondary Criteria Sorting: Once lengths are sorted, implement additional criteria such as lexicographic order for strings of equal length.
• In-built functions: Languages like Python include functions such as `sorted()` or `sort()`, which can take a `key` parameter to customize sorting logic.

When sorting a list of strings, you often first arrange them by length. Then, apply further sorting within groups of equal-length strings using lexicographic order, thus meeting complex sorting requirements that cater to multiple criteria.