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.

Follow up:

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

题目大意 #

判断一个整数是否是回文数。回文数是指正序（从左向右）和倒序（从右向左）读都是一样的整数。

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
}

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