LeetCode August - Day 3

Problem Statement

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:

Input: "A man, a plan, a canal: Panama"
Output: true

Example 2:

Input: "race a car"
Output: false

Constraints: s consists only of printable ASCII characters.

Inputs, Outputs, Constraints & Exceptions

• I: string {s}
• O: boolean
• C: - s is basic ASCII chars
  • s.length in range [0, 10000]
• E: - empty string
  • string of length 1
  • string of only special characters or spaces

Code

/**
 * @param {string} s
 * @return {boolean}
 */
function isPalindrome(s) {
  if(s.length <= 1){
    return true
  }

  let i = 0, j = s.length - 1;
  while(i <= j){
    if(!/[a-zA-Z0-9]/.test(s[i])){
      i++;
      continue;
    }

    if(!/[a-zA-Z0-9]/.test(s[j])){
      j--;
      continue;
    }

    if(s[i].toLocaleLowerCase() !== s[j].toLocaleLowerCase()){
      return false
    }
    
    i++;
    j--;
  }

  return true
};

Time complexity: O(N)
Space complexity: O(1)