Valid_palindrome

README

Given

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A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.

Given a string s, return true if it is a palindrome, or false otherwise.

Example 1:

Input: s = "A man, a plan, a canal: Panama"
Output: true
Explanation: "amanaplanacanalpanama" is a palindrome.

Example 2:

Input: s = "race a car"
Output: false
Explanation: "raceacar" is not a palindrome.

Example 3:

Input: s = " "
Output: true
Explanation: s is an empty string "" after removing non-alphanumeric characters.
Since an empty string reads the same forward and backward, it is a palindrome.

Constraints:

• 1 <= s.length <= 2 * 10^5
• s consists only of printable ASCII characters.

Solution

Golang solution

import (
    "regexp"
    "strings"
)

func reverse(s string) string {
    r := []rune(s)
    for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
        r[i], r[j] = r[j], r[i]
        }
    return string(r)
}

func isPalindrome(s string) bool {
    s = strings.ToLower(s)
    re, _ := regexp.Compile(`[^a-zA-Z0-9]+`)
    new_text := re.ReplaceAllString(s, "")
    return new_text == reverse(new_text)
}

Python solution

class Solution:
    def isPalindrome(self, s: str) -> bool:
        s = s.lower()
        # remove all non alphanumeric characters using isalnum()
        s = [c for c in s if c.isalnum()]
        return s == s[::-1]

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