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String Interview Questions

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

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Topics

String 112
StringClear all
3.Longest Substring Without Repeating Characters
Hash TableStringSliding Window
Medium+13▶ Mock
5.Longest Palindromic Substring
StringDynamic Programming
Medium+8▶ Mock
49.Group Anagrams
Hash TableStringSorting
Medium+9▶ Mock
20.Valid Parentheses
StackString
Easy+3▶ Mock
438.Find All Anagrams in a String
Hash TableStringSliding Window
Medium+2▶ Mock
Implement Trie (Prefix Tree)
TrieDesignString
Medium+2▶ Mock
91.Decode Ways
Dynamic ProgrammingString
Medium+4▶ Mock
22.Generate Parentheses
StringDynamic ProgrammingBacktracking
Medium+1▶ Mock
567.Permutation in String
Hash TableTwo PointersString
Medium▶ Mock
981.Time Based Key-Value Store
Hash TableStringBinary Search
Medium+1▶ Mock
14.Longest Common Prefix
ArrayStringTrie
Easy+1▶ Mock
76.Minimum Window Substring
Hash TableStringSliding Window
Hard▶ Mock
79.Word Search
ArrayStringBacktracking
Medium+1▶ Mock
13.Roman to Integer
Hash TableMathString
Easy+1▶ Mock
17.Letter Combinations of a Phone Number
Hash TableStringBacktracking
Medium+1▶ Mock
12.Integer to Roman
Hash TableMathString
Medium▶ Mock
399.Evaluate Division
ArrayStringDepth-First Search
Medium▶ Mock
44.Wildcard Matching
StringDynamic ProgrammingGreedy
Hard▶ Mock
721.Accounts Merge
ArrayHash TableString
Medium▶ Mock
125.Valid Palindrome
Two PointersString
Easy▶ Mock
8.String to Integer (atoi)
String
Medium▶ Mock
2408.Design SQL
ArrayHash TableString
Medium▶ Mock
67.Add Binary
MathStringBit Manipulation
Easy▶ Mock
516.Longest Palindromic Subsequence
StringDynamic Programming
Medium▶ Mock
424.Longest Repeating Character Replacement
Hash TableStringSliding Window
Medium▶ Mock
1143.Longest Common Subsequence
StringDynamic Programming
Medium▶ Mock
751.IP to CIDR
StringBit Manipulation
Medium▶ Mock
6.Zigzag Conversion
String
Medium▶ Mock
127.Word Ladder
Hash TableStringBreadth-First Search
Hard▶ Mock
68.Text Justification
ArrayStringSimulation
Hard▶ Mock
1839.Longest Substring Of All Vowels in Order
StringSliding Window
Medium▶ Mock
796.Rotate String
StringString Matching
Easy▶ Mock
3484.Design Spreadsheet
ArrayHash TableString
Medium▶ Mock
631.Design Excel Sum Formula
ArrayHash TableString
Hard▶ Mock
3043.Find the Length of the Longest Common Prefix
ArrayHash TableString
Medium▶ Mock
2062.Count Vowel Substrings of a String
Hash TableString
Easy▶ Mock
1138.Alphabet Board Path
Hash TableString
Medium▶ Mock
227.Basic Calculator II
MathStringStack
Medium▶ Mock
2484.Count Different Palindromic Subsequences
StringDynamic Programming
Hard▶ Mock
2559.Count Vowel Strings in Ranges
ArrayStringPrefix Sum
Medium▶ Mock
2353.Design a Food Rating System
ArrayHash TableString
Medium▶ Mock
2296.Design a Text Editor
Linked ListStringStack
Hard▶ Mock
588.Design In-Memory File System
Hash TableStringDesign
Hard▶ Mock
1396.Design Underground System
Hash TableStringDesign
Medium▶ Mock
115.Distinct Subsequences
StringDynamic Programming
Hard▶ Mock
72.Edit Distance
StringDynamic Programming
Medium▶ Mock
271.Encode and Decode Strings
ArrayStringDesign
Medium▶ Mock
32.Longest Valid Parentheses
StringDynamic ProgrammingStack
Hard▶ Mock
179.Largest Number
ArrayStringGreedy
Medium▶ Mock
28.Find the Index of the First Occurrence in a String
Two PointersStringString Matching
Easy▶ Mock
1048.Longest String Chain
ArrayHash TableTwo Pointers
Medium▶ Mock
2933.High-Access Employees
ArrayHash TableString
Medium▶ Mock
609.Find Duplicate File in System
ArrayHash TableString
Medium▶ Mock
564.Find the Closest Palindrome
MathString
Hard▶ Mock
1768.Merge Strings Alternately
Two PointersString
Easy▶ Mock
1249.Minimum Remove to Make Valid Parentheses
StringStack
Medium▶ Mock
3090.Maximum Length Substring With Two Occurrences
Hash TableStringSliding Window
Easy▶ Mock
131.Palindrome Partitioning
StringDynamic ProgrammingBacktracking
Medium▶ Mock
1366.Rank Teams by Votes
ArrayHash TableString
Medium▶ Mock
1209.Remove All Adjacent Duplicates in String II
StringStack
Medium▶ Mock
402.Remove K Digits
StringStackGreedy
Medium▶ Mock
767.Reorganize String
Hash TableStringGreedy
Medium▶ Mock
93.Restore IP Addresses
StringBacktracking
Medium▶ Mock
3035.Maximum Palindromes After Operations
ArrayHash TableString
Medium▶ Mock
3387.Maximize Amount After Two Days of Conversions
ArrayStringDepth-First Search
Medium▶ Mock
1639.Number of Ways to Form a Target String Given a Dictionary
ArrayStringDynamic Programming
Hard▶ Mock
1915.Number of Wonderful Substrings
Hash TableStringBit Manipulation
Medium▶ Mock
678.Valid Parenthesis String
StringDynamic ProgrammingStack
Medium▶ Mock
443.String Compression
Two PointersString
Medium▶ Mock
692.Top K Frequent Words
ArrayHash TableString
Medium▶ Mock
71.Simplify Path
StringStack
Medium▶ Mock
737.Sentence Similarity II
ArrayHash TableString
Medium▶ Mock
2380.Time Needed to Rearrange a Binary String
StringDynamic ProgrammingSimulation
Medium▶ Mock
2213.Longest Substring of One Repeating Character
ArrayStringSegment Tree
Hard▶ Mock
332.Reconstruct Itinerary
ArrayStringDepth-First Search
Hard▶ Mock
428.Serialize and Deserialize N-ary Tree
StringTreeDepth-First Search
Hard▶ Mock
2096.Step-By-Step Directions From a Binary Tree Node to Another
StringTreeDepth-First Search
Medium▶ Mock
664.Strange Printer
StringDynamic Programming
Hard▶ Mock
1258.Synonymous Sentences
ArrayHash TableString
Medium▶ Mock
2434.Using a Robot to Print the Lexicographically Smallest String
Hash TableStringStack
Medium▶ Mock
1236.Web Crawler
StringDepth-First SearchBreadth-First Search
Medium▶ Mock
140.Word Break II
ArrayHash TableString
Hard▶ Mock
Valid Anagram
Hash TableStringSorting
Easy▶ Mock
Design Add and Search Words Data Structure
StringDepth-First SearchDesign
Medium▶ Mock
Word Search II
ArrayStringBacktracking
Hard+1▶ Mock
43.Multiply Strings
MathStringSimulation
Medium▶ Mock
65.Valid Number
String
Hard▶ Mock
166.Fraction to Recurring Decimal
Hash TableMathString
Medium▶ Mock
205.Isomorphic Strings
Hash TableString
Easy▶ Mock
243.Shortest Word Distance
ArrayString
Easy▶ Mock
244.Shortest Word Distance II
ArrayHash TableTwo Pointers
Medium▶ Mock
257.Binary Tree Paths
StringBacktrackingTree
Easy▶ Mock
282.Expression Add Operators
MathStringBacktracking
Hard▶ Mock
340.Longest Substring with At Most K Distinct Characters
Hash TableStringSliding Window
Medium▶ Mock
383.Ransom Note
Hash TableStringCounting
Easy▶ Mock
387.First Unique Character in a String
Hash TableStringQueue
Easy▶ Mock
394.Decode String
StringStackRecursion
Medium▶ Mock
642.Design Search Autocomplete System
StringDepth-First SearchDesign
Hard▶ Mock
657.Robot Return to Origin
StringSimulation
Easy▶ Mock
696.Count Binary Substrings
Two PointersString
Easy▶ Mock
838.Push Dominoes
Two PointersStringDynamic Programming
Medium▶ Mock
1055.Shortest Way to Form String
Two PointersStringBinary Search
Medium▶ Mock
1087.Brace Expansion
StringBacktrackingBreadth-First Search
Medium▶ Mock
1202.Smallest String With Swaps
ArrayHash TableString
Medium▶ Mock
1297.Maximum Number of Occurrences of a Substring
Hash TableStringSliding Window
Medium▶ Mock
1347.Minimum Number of Steps to Make Two Strings Anagram
Hash TableStringCounting
Medium▶ Mock
1963.Minimum Number of Swaps to Make the String Balanced
Two PointersStringStack
Medium▶ Mock
2232.Minimize Result by Adding Parentheses to Expression
StringEnumeration
Medium▶ Mock
2243.Calculate Digit Sum of a String
StringSimulation
Easy▶ Mock
2914.Minimum Number of Changes to Make Binary String Beautiful
String
Medium▶ Mock
3076.Shortest Uncommon Substring in an Array
ArrayHash TableString
Medium▶ Mock
3078.Match Alphanumerical Pattern in Matrix I
ArrayHash TableString
Medium▶ Mock

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