The term alien in the context of programming language basically relates to an unknown language with an unspecified number of characters that need to be arranged in the correct order to be understood properly.

Now, these characters are contained within an alien dictionary that can be iterated within a program using different approaches and algorithms

An alien dictionary essentially consists of a series of characters that are initially arranged in a jumbled order that ultimately makes it difficult to understand the language

In this blog, let’s have a look at some of the top algorithms that can be applied for finding the right order of characters within an alien dictionary.

What Do You Mean by Alien Dictionary?

Before learning what is an alien dictionary, let us look at the context in which the word “alien” is being used:

“In this context, the word Alien refers to something that is completely unknown”.

The concept of the alien dictionary is essentially derived from the fact that programming languages usually consist of thousands of unknown languages that do not have a specific order or arrangement amongst their characters.

This is why the special characters and symbols of these unknown languages are often stored in alien dictionaries.

Although, dealing with these sorts of languages may or may not usually have pre-determined rules. In a problem statement that concerns an alien directory, the words are always lexically arranged pertaining to the rules of the new language.

This type of problem statement usually relates to finding out the position and arrangement of the characters and, ultimately assigning them the correct order by running specific functions within the program.

Now, since we have mentioned the term characters ample amount of time in this short description, let us have a look at what it essentially means in the context of alien dictionaries.

What are “Characters” in an Alien Dictionary?

Well, the characters of an alien dictionary are essentially referred to the alphabets of the dictionary otherwise commonly known as words.

Check out the following input of characters for clear understanding:

Words- “cad”, “cab”, “abca”, “acbd”, “baa”

This arrangement might seem simple but deriving an output in the form of a foreign language from within the alien dictionaries can be a massively complex process if one is not acquainted with the proper algorithms.

To save you from the trouble of finding the appropriate methods, we have compiled the following section that mentions the problem statement concerning alien dictionaries.

Along with that, we have also discussed prospective approaches with their concerned time complexities that can be used for solving this problem statement.

So let’s discuss the algorithms together!

How Would You Find The Order Of Characters From Alien Dictionary?

Before we head on to the main content of the blog which is the possible approaches, let’s consider a problem statement related to alien dictionaries.

Problem Statement:

You have been provided a sorted dictionary i.e an arrangement of words from an alien language. Your task is to figure out the right order that should be used for the arrangement of these characters.

For problems concerning alien dictionaries, we usually apply the following approaches:

• Topological sorting

This approach essentially focuses on creating a linear order of the vertices within a directed graph and returning the array in such a form that the nodes contained within the array shall appear before the nodes that they are pointing towards.

• By Comparing the Invalid Input Data

This is a general comparison algorithm that we will be using in the context of C++ for this particular program. The algorithm for this approach will be implemented by performing a comparison between two adjacent words of the alien dictionary at a time.

This process will continue to run until all the words contained within the dictionary have been assessed and compared.

That said, let us discuss the implementation of both these and their respective time complexities and other components that follow.

Method 1: Implementing the Topological Sorting Algorithm

The initial idea for this approach is to create a graph consisting of all the characters from the alien dictionary. After this, we will be further implementing a topological sorting of the graph structure that has been created.

Here’s how the algorithm for this should work:

• Start by creating a graph g. The vertices of the graph should replicate the size of the alphabets arranged within the given alien dictionary.
• For instance, let us consider that the size of the alphabet within the dictionary is 4. This would imply that there will only be 4 characters within each word.
• Also, this graph will be exempted from having any edges.
• Next up, you will have to perform two functions for each of the adjacent pairs of words contained within the dictionary or array.
• Initially, we will start by considering the words “word 1” and “word 2”.
• These words will be matched for every existing character to figure out the placement of the mismatched character.
• Once it has been found we will be creating an edge in graph g for storing the mismatched characters.
• Finally, once the process is completed, the topological sorting will be printed of the created graph.

Time Complexity for this Approach:

The time complexity would be- O(n+alpha).

Method 2: Comparing Adjacent Words In Case Of Invalid Input Data

This algorithm can be implemented in C++ programming efficiently.

Here’s how the algorithm would go for this approach:

• Similar to the first approach, compare adjacent words such as word 1. word 2 and so on.
• Then in the next round, we will be comparing each character individually for every pair of adjacent words.
• We will continue the process until we identify the first mismatched word.
• This process will be projected on all the pairs of adjacent words until we have analyzed all the words.
• Once the process is completed we will call “Alien characters” and this class will take care of the entire sorting problem.

Time Complexity for This Approach:

O(N*L)

Wrapping Up

Destroying the barrier of understanding foreign or alien languages is definitely one of the greatest problems solved by programming.

The effective use of alien dictionaries in coding remains an effective testimony to this fact. That said, the concepts of Hashmaps and Binary Trees have proved to be highly effective in arranging the contents of an alien dictionary.

Learn more about Hashing Algorithms and Mirror Binary Trees from our other blogs!

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