Group Anagrams Using Hash Map in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an anagram?

An anagram is a word or phrase formed by rearranging the letters of another word or phrase, using all the original letters exactly once.

beginner

Why do we use a hash map to group anagrams?

We use a hash map to group anagrams because it allows us to store words with the same sorted letters as the key, making it easy to collect all anagrams together efficiently.

beginner

How do you create a key for the hash map when grouping anagrams?

You create the key by sorting the letters of the word alphabetically. For example, 'eat' becomes 'aet'. All anagrams share the same sorted key.

intermediate

What is the time complexity of grouping anagrams using a hash map?

The time complexity is O(N * K log K), where N is the number of words and K is the maximum length of a word, because sorting each word takes O(K log K).

beginner

Explain the main steps to group anagrams using a hash map.

1. Initialize an empty hash map.<br>2. For each word, sort its letters to create a key.<br>3. Add the original word to the list of values for that key.<br>4. After processing all words, the hash map values are groups of anagrams.

What is the key used in the hash map when grouping anagrams?

A The original word itself

B The length of the word

C The first letter of the word

D The sorted letters of the word

The key is the sorted letters of the word because all anagrams share the same sorted letter sequence.

Which data structure is best for grouping anagrams efficiently?

A Stack

B Queue

C Hash map (dictionary)

D Linked list

A hash map allows quick grouping by keys, making it ideal for grouping anagrams.

What is the main operation done on each word to find its group?

A Sorting the letters

B Reversing the word

C Counting vowels

D Finding the length

Sorting the letters creates a uniform key for all anagrams.

If the input list is ['bat', 'tab', 'eat', 'tea'], how many groups of anagrams will be formed?

A 1

B 2

C 3

D 4

There are two groups: ['bat', 'tab'] and ['eat', 'tea'].

What is the output format after grouping anagrams?

A A list of lists, each containing anagrams

B A single string with all words

C A sorted list of words

D A count of anagrams

The output is a list of lists, where each inner list contains words that are anagrams of each other.

Describe how you would group a list of words into anagrams using a hash map.

Think about how sorting helps identify anagrams.

Explain why sorting each word is important in grouping anagrams.

Consider what makes anagrams similar.