### LeetCode 9. Palindrome Number

9.Palindrome Number

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.

求出回文数对比

将数字反转进行对比。可以参考LeetCode 7

public boolean isPalindrome(int x) {
    if(x < 0){
        return false;
    }
    
    int res = 0;
    int y = x;
    while(y != 0){          
        res = res* 10 + (y % 10);
        y = y/10;
    }
    
    return x==res;
}

数字转字符串

将数字转换成字符串，然后使用两个指针。

    if(x < 0 || x >= Integer.MAX_VALUE){
        return false;
    }
    String s = String.valueOf(x);
    int len = s.length();
    int left = 0;
    int right = len -1;
    while(left < right){
        if(s.charAt(left) != s.charAt(right)){
            return false;
        }  
        left++;
        right--;
    }
    return true;
    
}