9. Palindrome Number

Link

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?

Solution

    public static boolean isPalindrome(int x) {
        if(x < 0 || (x !=0 && x%10 == 0)) return false; //Remember every none-zero number end with 0 can't be a palindrome
        //transit half of x to palindrome and compare it with another side
        int palindrome = 0;
        while(x > palindrome){
            palindrome = palindrome*10 + (x%10);
            x = x/10;
        }
        //for even and odd cases
        return (palindrome == x) || (x == palindrome/10);
    }