Group Anagrams
Group strings that are anagrams of each other.
Pattern fit
The core is designing a canonical signature for character counts, which is a cousin of prefix/frequency counting rather than a traversal problem.
Key observation
Two strings belong to the same group exactly when their normalized character-count signatures match.
Target complexity
O(total chars) / O(n)
How to break down the solution cleanly
The core is designing a canonical signature for character counts, which is a cousin of prefix/frequency counting rather than a traversal problem.
Two strings belong to the same group exactly when their normalized character-count signatures match.
Define what the cumulative state means.
Build the prefix in one forward pass.
Reference implementation
Python# Generic pattern template
prefix = [0] * (len(nums) + 1)
for i, value in enumerate(nums):
prefix[i + 1] = prefix[i] + value
range_sum = prefix[r + 1] - prefix[l]
Common pitfalls
Using the unsorted string itself as the key.
Building a key that is ambiguous across different count tuples.
Common follow-ups
Would sorted-string keys or count-vector keys be better here?
How would this change for Unicode-heavy inputs?
Continue with related problems
Build repeatable depth inside the Prefix Sum cluster before moving on.