Leetcode Palindrome Number

Determine whether an integer is a palindrome. Do this without extra space.

click to show spoilers.

Some hints:

Could negative integers be palindromes? (ie, -1)

If you are thinking of converting the integer to string, note the restriction of using extra space.

You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How would you handle such case?

There is a more generic way of solving this problem.

---

解题思路：

直接判断第一个和最后一个，循环往复。这样就不会对数字进行修改，而只是判断而已。

---

 Java code:

public boolean isPalindrome(int x) {
        if(x < 0 ) {return false;} //negative numbers are not palindrome
        
        int div =1;
        while(x/div >=10) {
            div *=10;
        }

        //compare left and right digit number
        while(x!=0) {
            int left = x/div;
            int right = x%10;
            if(left != right) {
                return false;
            }
            x = (x%div)/10;
            div /=100;
        }
        return true;
    }

---

Reference:

1. http://www.cnblogs.com/springfor/p/3889214.html