9. Palindrome Number
难度: Easy
刷题内容
原题连接
- https://leetcode.com/problems/palindrome-number
内容描述
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?
解题方案
思路 1 **- 时间复杂度: O(log2 N)*- 空间复杂度: O(1)***
- 不使用字符串,使用除法分别从首尾获得数字，最后对比是否相同
代码：
/**
* @param {number} x
* @return {boolean}
*/
var isPalindrome = function(x) {
if(x<0||x!==0&&x%10===0)
return false;
var reverse = 0;
while (x>reverse){
reverse = reverse*10 +x%10;
x = Math.floor(x/10);
}
return reverse === x||Math.floor(reverse/10) === x;
};
思路 2 **- 时间复杂度: O(N)*- 空间复杂度: O(N)***
- 转化为字符串，reverse字符串
代码：
var isPalindrome = function(x) {
return x.toString().split('').reverse().join('')==x.toString()?true:false;
};
