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2. Strings

Easy

1. Count Vowels:

  • Write a function that takes a string and returns the number of vowels in the string.

Test cases:

  • countVowels('hello') -> 2
  • countVowels('world') -> 1
  • countVowels('aeiou') -> 5
  • countVowels('bcdfg') -> 0
  • countVowels('') -> 0

2.Palindrome Check:

  • Write a function that takes a string and returns true if the string is a palindrome, and false otherwise.

Test cases:

  • isPalindrome('madonna') -> false
  • isPalindrome('madam') -> true
  • isPalindrome('racecar') -> true
  • isPalindrome('hello') -> false
  • isPalindrome('') -> true

3. Reverse String:

  • Write a function that takes a string and returns the string reversed.

Test cases:

  • reverseString('hello') -> olleh
  • reverseString('world') -> dlrow
  • reverseString('') -> ``
  • reverseString('a') -> a
  • reverseString('abcd') -> dcba

Medium

4. Anagram Check:

  • Write a function that takes two strings and returns true if they are anagrams of each other, and false otherwise.

Test cases:

  • isAnagram('listen', 'silent') -> true
  • isAnagram('hello', 'world') -> false
  • isAnagram('evil', 'vile') -> true
  • isAnagram('fluster', 'restful') -> true
  • isAnagram('example', 'sample') -> false

5. Capitalize Words:

  • Write a function that takes a string and returns the string with the first letter of each word capitalized.

Test cases:

  • capitalizeWords('hello world') -> Hello World
  • capitalizeWords('javascript is fun') -> Javascript Is Fun
  • capitalizeWords('') -> ``
  • capitalizeWords('a quick brown fox') -> A Quick Brown Fox
  • capitalizeWords('capitalize') -> Capitalize

6. Longest Substring Without Repeating Characters:

  • Write a function that takes a string and returns the length of the longest substring without repeating characters.

Test cases:

  • lengthOfLongestSubstring('abcabcbb') -> 3
  • lengthOfLongestSubstring('bbbbb') -> 1
  • lengthOfLongestSubstring('pwwkew') -> 3
  • lengthOfLongestSubstring('') -> 0
  • lengthOfLongestSubstring('aab') -> 2

7. String Compression:

  • Write a function that takes a string and returns a compressed version (e.g., "aabcccccaaa" to "a2b1c5a3").

Test cases:

  • compressString('aabcccccaaa') -> a2b1c5a3
  • compressString('abc') -> abc
  • compressString('aaaaa') -> a5
  • compressString('aabbcc') -> a2b2c2
  • compressString('') -> ``

Hard

8. Longest Palindromic Substring:

  • Write a function that takes a string and returns the longest palindromic substring.

Test cases:

  • longestPalindrome('babad') -> bab or aba
  • longestPalindrome('cbbd') -> bb
  • longestPalindrome('a') -> a
  • longestPalindrome('ac') -> a or c
  • longestPalindrome('racecar') -> racecar

9. Wildcard Matching:

  • Write a function that takes a string and a pattern (with ? and * wildcards) and returns true if the string matches the pattern.

Test cases:

  • wildcardMatch('aa', 'a') -> false
  • wildcardMatch('aa', '*') -> true
  • wildcardMatch('cb', '?a') -> false
  • wildcardMatch('adceb', 'ab') -> true
  • wildcardMatch('acdcb', 'a*c?b') -> false

10. Regex Parser:

  • Write a function that takes a string and a regex pattern and returns whether the string matches the pattern.

Test cases:

  • regexParser('abc', '^a.c$') -> true
  • regexParser('abc', '^a.d$') -> false
  • regexParser('hello', 'h.llo') -> true
  • regexParser('hello', 'h.*o') -> true
  • regexParser('hello', '^h.*d$') -> false