0009. Palindrome Number

# 9. Palindrome Number#

## 题目 #

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

Example 1:

``````Input: 121
Output: true
``````

Example 2:

``````Input: -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: 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
``````

Coud you solve it without converting the integer to a string?

## 解题思路 #

• 判断一个整数是不是回文数。
• 简单题。注意会有负数的情况，负数，个位数，10 都不是回文数。其他的整数再按照回文的规则判断。

## 代码 #

``````
package leetcode

import "strconv"

// 解法一
func isPalindrome(x int) bool {
if x < 0 {
return false
}
if x == 0 {
return true
}
if x%10 == 0 {
return false
}
arr := make([]int, 0, 32)
for x > 0 {
arr = append(arr, x%10)
x = x / 10
}
sz := len(arr)
for i, j := 0, sz-1; i <= j; i, j = i+1, j-1 {
if arr[i] != arr[j] {
return false
}
}
return true
}

// 解法二 数字转字符串
func isPalindrome1(x int) bool {
if x < 0 {
return false
}
if x < 10 {
return true
}
s := strconv.Itoa(x)
length := len(s)
for i := 0; i <= length/2; i++ {
if s[i] != s[length-1-i] {
return false
}
}
return true
}

``````

Apr 8, 2023