6 articles
LeetCode 187 Repeated DNA Sequences — find every 10-letter substring that appears twice or more. Encode each nucleotide in 2 bits, slide a 20-bit window with shift and AND. Linear-time bit manipulation interview classic.
Rabin Karp uses a polynomial rolling hash to fingerprint each window of the text and matches against the pattern hash in expected O(n + m) time. Master this and you unlock substring search, plagiarism detection, and the entire family of hash-based string problems.
Group anagrams, find anagram occurrences, and detect anagrams under constraints. Master the three classical encodings — sorted key, 26-bucket frequency vector, and prime-product hash — with rolling-window extensions used at Meta and Google.
Shortest Palindrome (LC 214) is a hard FAANG problem that hides a classic KMP application. Concatenate s with reversed(s) and the failure function reveals the longest palindromic prefix in linear time. Master this trick and you unlock half a dozen related KMP applications.
Counting distinct substrings of a string is the gateway problem to suffix arrays and suffix automata. Three classical solutions — n^2 hash set, suffix array plus LCP, and suffix automaton — span the full toolbox of competitive programming and FAANG hard interviews.
Complete recap of all 20 string algorithm problems: pattern recognition guide, algorithm selection, complexity reference, and interview strategy for FAANG string questions.