Palindrome

A palindrome is a word or phrase that reads the same forward as it does backward. Some of the simple examples are "kayak", "Hannah" and "refer" if we would like to know how do palindromic words look like. There are also palindrome-like phrases such as "Dennis and Edna sinned" and "Draw pupil's lip upward".

It would not be too difficult to determine algorithmically if a word or sentence is a palindrome. There are many ways to solve it but we also need to consider if our solution is not computationally expensive.

I have thought of a simple and yet an efficient solution to our discussion. This is a static method that strips off the punctuations and also white character spacings. The method returns a boolean value true if the input string is a palindrome otherwise it returns false.

public static boolean isPalindrome(String text){
  //Sets an index at the far left of the word or phrase
  int leftIndex = 0;

  //Converts input text into lower case and remove
  //any single non-alphanumeric and underscore
  text = text.toLowerCase().replaceAll("[\\W\\_*]", "");

  //Sets an index at the far right of the word or phrase
  int rightIndex = text.length()-1;
  while (leftIndex < rightIndex) {
    if (!(text.charAt(leftIndex) == text.charAt(rightIndex))) {
      //returns a false and get out from the while loop
      return false;
    }

    //gets the indexes from both sides closer
    leftIndex++;
    rightIndex--; 
  }
  //returns a true if all the characters mirrors to each other
  return true;
}