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Palindrome Permutation Mystery in Ruby: Detecting Whether a String Can Be Rearranged into a Palindrome

   January 30, 2024
Ruby @ Freshers.in

Palindromes, those enigmatic sequences that read the same forwards and backwards, have fascinated mathematicians and linguists for centuries. In this article, we’ll explore how to create a Ruby function to determine if a given string can be rearranged into a palindrome. Detecting palindrome permutations is a valuable skill in programming and can be used in various applications, including text processing and string manipulation.

Understanding Palindrome Permutations

A palindrome is a word or phrase that remains the same when its characters are reversed. For example, “racecar” and “madam” are palindromes. A palindrome permutation is a string that can be rearranged to form a palindrome. For instance, “civic” can be rearranged into “civic,” making it a palindrome permutation.

The Ruby Function

Let’s start by defining a Ruby function called can_rearrange_to_palindrome to check if a given string can be rearranged into a palindrome.

def can_rearrange_to_palindrome(str)
  char_count = {}
  # Count the frequency of each character
  str.each_char do |char|
    char_count[char] ||= 0
    char_count[char] += 1
  end
  # Check if there is at most one character with an odd frequency
  odd_count = 0
  char_count.values.each do |count|
    odd_count += 1 if count.odd?
    return false if odd_count > 1
  end
  return true
end

Example Usage

Now, let’s explore some examples to see how our can_rearrange_to_palindrome function works:

input_str_1 = "civic"
result_1 = can_rearrange_to_palindrome(input_str_1)
puts "Input String: #{input_str_1}"
puts "Can be rearranged into a palindrome? #{result_1}"

Output:

Input String: civic
Can be rearranged into a palindrome? true

In this example, “civic” can be rearranged into a palindrome, so the function returns true.

Another Example:

input_str_2 = "hello"
result_2 = can_rearrange_to_palindrome(input_str_2)
puts "Input String: #{input_str_2}"
puts "Can be rearranged into a palindrome? #{result_2}"

Output:

Input String: hello
Can be rearranged into a palindrome? false

Here, “hello” cannot be rearranged into a palindrome, so the function returns false.

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