leetcode Algorithmic Question 125 (Simple 033) Roman Number to Integer

• Topic introduction

Given a string, verify that it is a palindrome string, only letters and numeric characters are considered, and the case of letters can be ignored.
Note: In this topic, we define empty strings as valid palindrome strings.

• Example

• Solution one

/**
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function(s) {
  let start = 0, end = s.length - 1;
  while (start < end) {
    while(start < end && isSymbol(s.charCodeAt(start))) {
        start++;
    }
    while(start < end && isSymbol(s.charCodeAt(end))) {
        end--;
    }
    if(start >= end) {
        return true;
    }
    if(!isEqual(s.charCodeAt(start), s.charCodeAt(end))) {
      return false;
    }
    start++;
    end--;
  }
  return true;
};

const isSymbol = ascii => {
  return ascii < 48 || ascii > 122 || (ascii > 57 && ascii < 65) || (ascii > 90 && ascii < 97);
}

const isEqual = (ascii1, ascii2) => {
  if(ascii1 === ascii2) {
    return true;
  }
  if(ascii1 <=57 || ascii2 <= 57) {
    return false;
  }
  return Math.abs(ascii1 - ascii2) === 32;
}

• Solution two

/**
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function(s) {
  let start = 0, end = s.length - 1;
  s = s.toLocaleLowerCase();
  while (start < end) {
    while(start < end && isSymbol(s.charAt(start))) {
        start++;
    }
    while(start < end && isSymbol(s.charAt(end))) {
        end--;
    }
    if(start >= end) {
        return true;
    }
    if(s.charAt(start) !== s.charAt(end)) {
      return false;
    }
    start++;
    end--;
  }
  return true;
};

const isSymbol = c => {
  return '0123456789abcdefghijklmnopqrstuvwxyz'.indexOf(c) === -1;
}

• Solution three

/**
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function(s) {
  s = s.replace(/[^a-zA-Z0-9]/g, '').toLocaleLowerCase();
  return s === s.split('').reverse().join('');
  // return s.replace(/[^a-zA-Z0-9]/g, '').toLocaleLowerCase() === s.replace(/[^a-zA-Z0-9]/g, '').toLocaleLowerCase().split('').reverse().join('');
};