•PRACTICE

String Interview Questions

85 String problems asked across FAANG and top tech companies. Approach hints, optimal solutions, and related problems.

Filter by company

Clear all ✕
Adobe (3)Amazon (14)Anthropic (2)Apple (16)Atlassian (13)Databricks (7)Google (14)Meta (17)Microsoft (16)Netflix (5)OpenAI (7)Oracle (14)Ripple (2)Rippling (11)Salesforce (13)Uber (9)Walmart (14)

Filter by topic

Array (178)Backtracking (17)BFS (23)Binary Search (34)Binary Tree (13)Bit Manipulation (16)Breadth-First Search (20)Counting (7)Data Stream (6)Database (6)Depth-First Search (27)Design (37)DFS (24)Divide and Conquer (7)Doubly-Linked List (5)DP (10)Dynamic Programming (39)Graph (6)Graph Theory (13)Greedy (31)Hash Table (87)Heap (12)Heap (Priority Queue) (13)Linked List (15)Math (32)Matrix (22)Monotonic Stack (6)Ordered Set (8)Prefix Sum (11)Queue (10)Recursion (7)Simulation (11)Sliding Window (21)Sorting (45)Stack (24)String (85)Topological Sort (6)Tree (30)Trie (10)Two Pointers (30)Union-Find (13)
🔒

to save your progress.

✓ 0ProblemDifficultyCompaniesBreakdown / SolutionLeetCode
Longest Substring Without Repeating CharactersMedium11 companiesView breakdown →
Longest Palindromic SubstringMedium9 companiesView breakdown →
Group AnagramsMedium8 companiesView breakdown →
Valid ParenthesesEasy5 companiesView breakdown →
Find All Anagrams in a StringMedium6 companiesView breakdown →
Implement Trie (Prefix Tree)Medium6 companiesView breakdown →
Decode WaysMedium7 companiesView breakdown →
Generate ParenthesesMedium4 companiesView breakdown →
Permutation in StringMedium3 companiesView breakdown →
Time Based Key-Value StoreMedium5 companiesView breakdown →
Longest Common PrefixEasy4 companiesView breakdown →
Minimum Window SubstringHard4 companiesView breakdown →
Word SearchMedium4 companiesView breakdown →
Roman to IntegerEasy4 companiesView breakdown →
Letter Combinations of a Phone NumberMedium4 companiesView breakdown →
Integer to RomanMedium2 companiesView breakdown →
Evaluate DivisionMedium2 companiesView breakdown →
Wildcard MatchingHard2 companiesView breakdown →
Accounts MergeMedium2 companiesView breakdown →
Valid PalindromeEasy2 companiesView breakdown →
String to Integer (atoi)Medium2 companiesView breakdown →
Design SQLMedium1 companiesView breakdown →
Add BinaryEasy1 companiesView breakdown →
Longest Palindromic SubsequenceMedium1 companiesView breakdown →
Longest Repeating Character ReplacementMedium1 companiesView breakdown →
Longest Common SubsequenceMedium2 companiesView breakdown →
IP to CIDRMedium2 companiesView breakdown →
Zigzag ConversionMedium2 companiesView breakdown →
Word LadderHard2 companiesView breakdown →
Text JustificationHard2 companiesView breakdown →
Longest Substring Of All Vowels in OrderMedium1 companiesView breakdown →
Rotate StringEasy1 companiesView breakdown →
Design SpreadsheetMedium2 companiesView breakdown →
Design Excel Sum FormulaHard2 companiesView breakdown →
Find the Length of the Longest Common PrefixMedium1 companiesView breakdown →
Count Vowel Substrings of a StringEasy1 companiesView breakdown →
Alphabet Board PathMedium1 companiesView breakdown →
Basic Calculator IIMedium1 companiesView breakdown →
Count Different Palindromic SubsequencesHard1 companiesView breakdown →
Count Vowel Strings in RangesMedium1 companiesView breakdown →
Design a Food Rating SystemMedium1 companiesView breakdown →
Design a Text EditorHard1 companiesView breakdown →
Design In-Memory File SystemHard1 companiesView breakdown →
Design Underground SystemMedium1 companiesView breakdown →
Distinct SubsequencesHard1 companiesView breakdown →
Edit DistanceMedium1 companiesView breakdown →
Encode and Decode StringsMedium1 companiesView breakdown →
Longest Valid ParenthesesHARD1 companiesView breakdown →
Largest NumberMEDIUM1 companiesView breakdown →
Find the Index of the First Occurrence in a StringEASY1 companiesView breakdown →
Longest String ChainMEDIUM1 companiesView breakdown →
High-Access EmployeesMEDIUM1 companiesView breakdown →
Find Duplicate File in SystemMEDIUM1 companiesView breakdown →
Find the Closest PalindromeHARD1 companiesView breakdown →
Merge Strings AlternatelyEASY1 companiesView breakdown →
Minimum Remove to Make Valid ParenthesesMEDIUM1 companiesView breakdown →
Maximum Length Substring With Two OccurrencesEASY1 companiesView breakdown →
Palindrome PartitioningMEDIUM1 companiesView breakdown →
Rank Teams by VotesMEDIUM1 companiesView breakdown →
Remove All Adjacent Duplicates in String IIMEDIUM1 companiesView breakdown →
Remove K DigitsMEDIUM1 companiesView breakdown →
Reorganize StringMEDIUM1 companiesView breakdown →
Restore IP AddressesMEDIUM1 companiesView breakdown →
Maximum Palindromes After OperationsMEDIUM1 companiesView breakdown →
Maximize Amount After Two Days of ConversionsMEDIUM1 companiesView breakdown →
Number of Ways to Form a Target String Given a DictionaryHARD1 companiesView breakdown →
Number of Wonderful SubstringsMEDIUM1 companiesView breakdown →
Valid Parenthesis StringMedium1 companiesView breakdown →
String CompressionMEDIUM1 companiesView breakdown →
Top K Frequent WordsMEDIUM1 companiesView breakdown →
Simplify PathMEDIUM1 companiesView breakdown →
Sentence Similarity IIMEDIUM1 companiesView breakdown →
Time Needed to Rearrange a Binary StringMEDIUM1 companiesView breakdown →
Longest Substring of One Repeating CharacterHARD1 companiesView breakdown →
Reconstruct ItineraryHARD1 companiesView breakdown →
Serialize and Deserialize N-ary TreeHard1 companiesView breakdown →
Step-By-Step Directions From a Binary Tree Node to AnotherMedium1 companiesView breakdown →
Strange PrinterHard1 companiesView breakdown →
Synonymous SentencesMEDIUM1 companiesView breakdown →
Using a Robot to Print the Lexicographically Smallest StringMEDIUM1 companiesView breakdown →
Web CrawlerMEDIUM1 companiesView breakdown →
Word Break IIHard1 companiesView breakdown →
Valid AnagramEasy4 companiesView breakdown →
Design Add and Search Words Data StructureMedium4 companiesView breakdown →
Word Search IIHard5 companiesView breakdown →

Practice with a Mock Interview

Solve these String problems under real interview pressure with our AI interviewer.

Start Mock Interview →