Anagram Detector

Level: Beginner 15–30 min

Concepts: AlgorithmsStringsValidation

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Build an anagram detection system that can check pairs, filter lists, and group words by their anagram sets.

Requirements

Step 1: Pair Detection

Given two words, determine if they are anagrams of each other.

• An anagram uses exactly the same letters, the same number of times
• Comparison should be case-insensitive
• Spaces and punctuation are ignored
• A word is not an anagram of itself

Examples:

• "listen" and "silent" → true
• "hello" and "world" → false
• "Astronomer" and "Moon starer" → true
• "rail safety" and "fairy tales" → true
• "cat" and "cat" → false (same word)

Step 2: Find Anagrams in a List

Given a subject word and a list of candidates, return the candidates that are anagrams of the subject.

subject: "listen"
candidates: ["enlists", "google", "inlets", "banana", "silent"]
result: ["inlets", "silent"]

Step 3: Group Anagrams

Given a list of words, group them by their anagram sets.

input: ["eat", "tea", "tan", "ate", "nat", "bat"]
output: [["eat", "tea", "ate"], ["tan", "nat"], ["bat"]]

Test Cases

Pair detection:

Word A	Word B	Anagram?
"listen"	"silent"	true
"hello"	"world"	false
"cat"	"tac"	true
"cat"	"cat"	false
"Cat"	"tac"	true
""	""	false
"a"	"a"	false
"ab"	"ba"	true
"aab"	"abb"	false

Find anagrams:

Subject	Candidates	Result
"listen"	["silent", "tinsel"]	["silent", "tinsel"]
"listen"	["hello", "world"]	[]
"master"	["stream", "maters", "pigeon"]	["stream", "maters"]

Group anagrams:

Input	Groups
["eat", "tea", "ate"]	[["eat", "tea", "ate"]]
["abc", "def"]	[["abc"], ["def"]]
[]	[]

Bonus

• Find the longest anagram pair in a dictionary file
• Detect partial anagrams — words where one is an anagram of a substring of the other
• Generate all possible anagrams of a given word (permutations that are real words, given a dictionary)

Hint

The key insight: two words are anagrams if they have the same sorted characters. Sorting the letters of "listen" and "silent" both give "eilnst". This sorted form is the anagram “key” — use it for grouping and comparison.