Feat | Neetcode | RoadMap | #10 Valid Palindrome

README.md

@@ -78,4 +78,6 @@
   - [Task #6](src/neetcode/arrays-&-hashing/encode-and-decode-strings) - _Encode And Decode Strings_ - _[check the task](https://neetcode.io/problems/string-encode-and-decode)_
   - [Task #7](src/neetcode/arrays-&-hashing/product-of-array-except-self) - _Products of Array Except Self_ - _[check the task](https://neetcode.io/problems/products-of-array-discluding-self)_
   - [Task #8](src/neetcode/arrays-&-hashing/valid-sudoku) - _Valid Sudoku_ - _[check the task](https://neetcode.io/problems/valid-sudoku)_
-  - [Task #9](src/neetcode/arrays-&-hashing/longest-consecutive-sequence) - _Longest Consecutive Sequence_ - _[check the task](https://neetcode.io/problems/longest-consecutive-sequence)_
+  - [Task #9](src/neetcode/arrays-&-hashing/longest-consecutive-sequence) - _Longest Consecutive Sequence_ - _[check the task](https://neetcode.io/problems/longest-consecutive-sequence)_
+- Two Pointers
+  - [Task #10](src/neetcode/two-pointers/valid-palindrome) - _Valid Palindrome_ - _[check the task](https://neetcode.io/problems/is-palindrome)_

src/neetcode/two-pointers/valid-palindrome/solution.test.ts

@@ -0,0 +1,13 @@
+import { isPalindrome } from './solution';
+
+describe('Valid Palindrome | NeetCode RoadMap | Testcases', () => {
+  test('#1 Valid string', () => {
+    const s = 'Was it a car or a cat I saw?';
+    expect(isPalindrome(s)).toBe(true);
+  });
+
+  test('#2 Invalid string', () => {
+    const s = 'tab a cat';
+    expect(isPalindrome(s)).toBe(false);
+  });
+});

src/neetcode/two-pointers/valid-palindrome/solution.ts

@@ -0,0 +1,25 @@
+/**
+ * @param {string} s - input string
+ * @return {boolean} `true` if `s` is a palindrome, false otherwise
+ */
+export const isPalindrome = (s: string): boolean => {
+  const isAlphaNumeric = (char: string): boolean =>
+    (char >= 'a' && char <= 'z') || (char >= 'A' && char <= 'Z') || (char >= '0' && char <= '9');
+
+  let right = s.length - 1;
+  let left = 0;
+  while (left < right) {
+    while (left < right && !isAlphaNumeric(s[left])) {
+      left++;
+    }
+    while (left < right && !isAlphaNumeric(s[right])) {
+      right--;
+    }
+    if (s[left].toLowerCase() !== s[right].toLowerCase()) {
+      return false;
+    }
+    left++;
+    right--;
+  }
+  return true;
+};