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Nozibul Islam
Nozibul Islam

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String Data Structures and Algorithms: Essential Interview Questions

String Data Structures and Algorithms: Essential Interview Questions.

Mastering string-related data structures and algorithms is crucial for coding interviews, as they test problem-solving abilities and understanding of string manipulation techniques. Here’s a categorized list of common string problems, including basic operations, algorithms, and advanced manipulations that are commonly asked in interviews.

1. Basic String Operations

  • Reverse a String: Reverse the characters of a string in place.
  • Check if a String is a Palindrome: Verify if a string reads the same forward and backward.
  • Count Vowels and Consonants in a String: Calculate the number of vowels and consonants.
  • Check if Two Strings are Anagrams: Determine if two strings contain the same characters in different orders.
  • Remove All Occurrences of a Character: Eliminate a specified character from a string.
  • Find the First Non-Repeating Character: Identify the first character that does not repeat in the string.
  • Find the Last Non-Repeating Character: Locate the last character in the string that appears only once.
  • Convert a String to Uppercase/Lowercase: Change the case of all characters.
  • Remove Whitespace: Strip out all spaces and tabs from the string.
  • Count the Frequency of Each Character: Create a frequency map of characters.

2. String Matching and Searching

  • Implement Naive String-Matching Algorithm: Basic pattern-matching technique.
  • Knuth-Morris-Pratt (KMP) Algorithm: Efficiently find patterns using prefix tables.
  • Rabin-Karp Algorithm: Uses hashing for substring search.
  • Boyer-Moore Algorithm: Skips sections of text for faster pattern matching.
  • Find All Occurrences of a Pattern in a Text (Using KMP).
  • Find All Anagrams of a Pattern in a Text (Sliding Window): Locate all anagrams using a window of fixed size.
  • Find the Longest Prefix Suffix (LPS) Array: Preprocess for KMP.
  • Find the First Occurrence of a Substring.
  • Check if a String Contains Another String: Perform substring search.
  • Count the Number of Occurrences of a Pattern.

3. String Manipulation

  • Rotate a String by N Characters: Shift characters to the left or right.
  • Swap Two Characters in a String.
  • Remove Duplicates from a String: Ensure each character appears only once.
  • Replace All Occurrences of a Substring: Substitute a given substring with another.
  • Merge Two Strings Alternately.
  • Find the Longest Common Substring.
  • Find the Longest Common Prefix.
  • Find the Longest Repeating Substring.
  • Reverse Words in a String: Reverse the order of words.
  • Remove All Adjacent Duplicates.

4. String Transformations

  • Convert a String to an Integer/Float: Parse strings into numerical values.
  • Implement String Compression/Decompression.
  • Find the Minimum Window Substring Containing All Characters.
  • Find the Maximum Repeating Character.
  • Count Distinct Substrings in a String.
  • Implement a Simple Text Formatter.
  • Convert to Title Case/Camel Case.

5. String Algorithms

  • Implement a Trie: For efficient prefix-based searching.
  • Find the Longest Palindromic Substring: Use dynamic programming or expand around center technique.
  • Longest Common Subsequence (LCS).
  • Shortest Common Supersequence.
  • Minimum Insertions/Deletions for a Palindromic String.
  • Edit Distance (Levenshtein Distance).
  • Suffix Array/Tree Implementation.
  • Longest Increasing Subsequence in a String.

6. String Comparison

  • Compare Strings (Ignoring/Respecting Case).
  • Check if One String is a Rotated Version of Another.
  • Check if a String is a Subsequence.
  • Check if a String Contains Unique Characters.
  • Validate String as a Parentheses Sequence.

7. String Patterns and Regular Expressions

  • Implement Regular Expression Matching.
  • Find Substrings Using Regular Expressions.
  • Validate Email, Phone Number, and URL.
  • Extract Dates/Phone Numbers from a String.
  • Replace Words Using Regex.

8. String Rotations and Shifts

  • Check if One String is a Rotation of Another.
  • Rotate a String (Left/Right).
  • Find the Minimum/Maximum Rotations to Match.
  • Implement a Circular Buffer.
  • Shift Characters by N Positions.

9. Advanced String Manipulations

  • Encode and Decode Strings.
  • Implement a Basic Text Editor.
  • Find All Permutations/Combinations of a String.
  • Find the Smallest Window Substring.
  • Calculate Longest Common Prefix Length.

By understanding and practicing these problems, you'll be well-equipped to handle string-related challenges in coding interviews. Each category is designed to build skills progressively, ensuring a well-rounded mastery of string manipulation and pattern recognition. Happy coding!

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