leetcode 9. Palindrome Number

Seawolf

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?

First try, convert integer to string.

class Solution {
    public boolean isPalindrome(int x) {
        
        String a = String.valueOf(x);
        
        return a.equals(reverse(a));
        
    }
    
    public String reverse(String str){
        
        int len = str.length();
        
        String re = "";
        
        for(int i = 0; i< len; i++){
            
            re = str.substring(i,i+1) + re;
            
        }
        
        return re;
    }
}

Second try without converting the integer to string.

class Solution {
    public boolean isPalindrome(int x) {
        
        if(x < 0){
            
            return false;
        }
        
        
        return x == reverse(x);
        
    }
    
    public Integer reverse(int x){
        
        int result = 0;
        
        while(x != 0){
            
            result = result * 10 + x % 10;
            
            x = x/10;
        }
        
        return result;
    }
}