feat: add palindrome number solution

Author: marcode24

leetcode/palindrome-number/README.md

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+# Palindrome Number
+
+## Description

leetcode/palindrome-number/solution.js

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+// solve without converting to string
+const isPalindrome = (x) => {
+  if (x < 0) {
+    return false;
+  }
+
+  let reverse = 0;
+  const original = x;
+
+  while (x > 0) {
+    reverse = (reverse * 10) + (x % 10);
+    x = Math.floor(x / 10);
+  }
+
+  return original === reverse;
+};
+
+// solve by converting to string
+const isPalindrome2 = (x) => x.toString() === [...x.toString()].reverse().join('');
+
+module.exports = {
+  isPalindrome,
+  isPalindrome2,
+};

leetcode/palindrome-number/solution.test.js

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+const { isPalindrome, isPalindrome2 } = require('./solution');
+
+describe('Palindrome Number', () => {
+  const testCases = [
+    {
+      input: 121,
+      output: true,
+    },
+    {
+      input: -121,
+      output: false,
+    },
+    {
+      input: 10,
+      output: false,
+    },
+    {
+      input: -101,
+      output: false,
+    },
+  ];
+
+  it('should return a boolean type', () => {
+    expect(typeof isPalindrome(121)).toBe('boolean');
+    expect(typeof isPalindrome2(121)).toBe('boolean');
+  });
+
+  it.each(testCases)('should return $output', (testCase) => {
+    expect(isPalindrome(testCase.input)).toBe(testCase.output);
+    expect(isPalindrome2(testCase.input)).toBe(testCase.output);
+  });
+});