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In this post, you will find the solution for the **Valid Palindrome** **in C++, Java & Python-LeetCode problem**. We are providing the **correct and tested solutions** to coding problems present on **LeetCode**. If you are not able to solve any problem, then you can take help from our Blog/website.

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** Link for the Problem** – Valid Palindrome– LeetCode Problem

Valid Palindrome– LeetCode Problem

**Problem:**

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:trueExplanation:"amanaplanacanalpanama" is a palindrome.

**Example 2:**

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

**Example 3:**

Input:s = " "Output:trueExplanation: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.

Valid Palindrome– LeetCode Solutions

Valid Palindrome Solution in C++:

class Solution { public: bool isPalindrome(string s) { int l = 0; int r = s.length() - 1; while (l < r) { while (l < r && !isalnum(s[l])) ++l; while (l < r && !isalnum(s[r])) --r; if (tolower(s[l]) != tolower(s[r])) return false; ++l; --r; } return true; } };

Valid Palindrome Solution in Java:

class Solution { public boolean isPalindrome(String s) { int l = 0; int r = s.length() - 1; while (l < r) { while (l < r && !Character.isLetterOrDigit(s.charAt(l))) ++l; while (l < r && !Character.isLetterOrDigit(s.charAt(r))) --r; if (Character.toLowerCase(s.charAt(l)) != Character.toLowerCase(s.charAt(r))) return false; ++l; --r; } return true; } }

Valid Palindrome Solution in Python:

class Solution: def isPalindrome(self, s: str) -> bool: l = 0 r = len(s) - 1 while l < r: while l < r and not s[l].isalnum(): l += 1 while l < r and not s[r].isalnum(): r -= 1 if s[l].lower() != s[r].lower(): return False l += 1 r -= 1 return True