feat(maths): is palindrome number (TheAlgorithms#118)

* Is Palindrome Number

* Is Palindrome Number update

* Added tests and updated Directory.md

* updated Directory.md

* feat(maths): improvements & resolved changes

* feat: improves algorithm & adjusts tests

* feat: documents limitation

---------

Co-authored-by: Fatima <[email protected]>

Author: zFl4wless

DIRECTORY.md

@@ -29,6 +29,7 @@
   * [Is Even](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/is_even.ts)
   * [Is Leap Year](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/is_leap_year.ts)
   * [Is Odd](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/is_odd.ts)
+  * [Is Palindrome](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/is_palindrome.ts)
   * [Is Square Free](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/is_square_free.ts)
   * [Lowest Common Multiple](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/lowest_common_multiple.ts)
   * [Perfect Square](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/perfect_square.ts)

maths/is_palindrome.ts

@@ -0,0 +1,21 @@
+/**
+ * A function to see if a number is a palindrome.
+ * Note that if the reversed number is larger than MAX_SAFE_INTEGER, rounding errors may occur and the result may be incorrect.
+ * Time Complexity: O(log(n))
+ *
+ * @param number The input number.
+ * @return {boolean} Wether the number is a Palindrome or not.
+ */
+export const IsPalindrome = (number: number): boolean => {
+    if (number < 0 || (number % 10 === 0 && number !== 0)) {
+        return false;
+    }
+
+    let reversed: number = 0;
+    while (number > reversed) {
+        reversed = reversed * 10 + (number % 10);
+        number = Math.floor(number / 10);
+    }
+
+    return number === reversed || number === Math.floor(reversed / 10);
+};

maths/test/is_palindrome.test.ts

@@ -0,0 +1,10 @@
+import { IsPalindrome } from "../is_palindrome";
+
+describe("IsPalindrome", () => {
+  test.each([[5, true], [1234, false], [12321, true], [31343, false]])(
+    "correct output for %i",
+    (nums, expected) => {
+        expect(IsPalindrome(nums)).toBe(expected);
+      },
+  );
+});