Add answer for question n.9 - Math example

Author: joffilyfe

golang/9.go

@@ -0,0 +1,40 @@
+package golang
+
+/*
+Given an integer x, return true if x is a palindrome, and false otherwise.
+
+Example 1:
+
+Input: x = 121
+Output: true
+Explanation: 121 reads as 121 from left to right and from right to left.
+Example 2:
+
+Input: x = -121
+Output: false
+Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
+Example 3:
+
+Input: x = 10
+Output: false
+Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
+
+Constraints: -231 <= x <= 231 - 1
+
+Follow up: Could you solve it without converting the integer to a string?
+*/
+func isPalindrome(x int) bool {
+
+	if x < 0 || (x%10 == 0 && x != 0) {
+		return false
+	}
+
+	rev := 0
+
+	for x > rev {
+		rev = rev*10 + x%10
+		x = x / 10
+	}
+
+	return x == rev || x == rev/10
+}

golang/9_test.go

@@ -0,0 +1,30 @@
+package golang
+
+import "testing"
+
+func TestFirstIsPalindrome(t *testing.T) {
+	input := 1221
+	result := isPalindrome(input)
+
+	if !result {
+		t.Errorf(`isPalindrome(%v) = %v expected return %v`, input, result, true)
+	}
+}
+
+func TestSecondIsPalindrome(t *testing.T) {
+	input := -1221
+	result := isPalindrome(input)
+
+	if result {
+		t.Errorf(`isPalindrome(%v) = %v expected return %v`, input, result, false)
+	}
+}
+
+func TestThirdIsPalindrome(t *testing.T) {
+	input := 10
+	result := isPalindrome(input)
+
+	if result {
+		t.Errorf(`isPalindrome(%v) = %v expected return %v`, input, result, false)
+	}
+}

golang/README.md

@@ -1,6 +1,7 @@
 | Problem Number | Tag                            | URL                                                                                  |
 | -------------- | ------------------------------ | ------------------------------------------------------------------------------------ |
 | 2.go           | Linked List                    | https://leetcode.com/problems/add-two-numbers/                                       |
+| 9.go           | Math                           | https://leetcode.com/problems/palindrome-number                                      |
 | 760.go         | Hash table                     | https://leetcode.com/problems/find-anagram-mappings/                                 |
 | 888.go         | Hash table                     | https://leetcode.com/problems/fair-candy-swap                                        |
 | 1165.go        | Hash table                     | https://leetcode.com/problems/single-row-keyboard/                                   |