Add 9 palindrome number

typescript/src/9-palindrome-number.ts

@@ -0,0 +1,47 @@
+export const isPalindrome = (x: number): boolean => {
+  if (x < 0) return false
+  const str = x.toString()
+
+  let left = 0
+  let right = str.length - 1
+
+  while (left <= right) {
+    if (str.charAt(left) === str.charAt(right)) {
+      left++
+      right--
+    } else {
+      return false
+    }
+  }
+
+  return true
+}
+
+export const isPalindromeImproved = (x: number): boolean => {
+  if (x < 0) return false
+
+  let temp = x
+  let y = 0
+  while (temp > 0) {
+    const last_num = temp % 10
+    temp = Math.floor(temp / 10)
+    y = y * 10 + last_num
+  }
+  return y == x
+}
+
+if (import.meta.vitest) {
+  const { test, expect } = import.meta.vitest
+  test('test one', () => {
+    expect(isPalindrome(121)).toBe(true)
+    expect(isPalindromeImproved(121)).toBe(true)
+  })
+  test('test two', () => {
+    expect(isPalindrome(-121)).toBe(false)
+    expect(isPalindromeImproved(-121)).toBe(false)
+  })
+  test('test three', () => {
+    expect(isPalindrome(10)).toBe(false)
+    expect(isPalindromeImproved(10)).toBe(false)
+  })
+}