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Leetcode 9 Palindrome Number.

Leetcode 9 Palindrome Number

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

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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.


It can be solved as you separate the number into two parts, the first half and second half.

If you rebuild the right half and compare that with the first half, and they are the same, then, you can know you should return TRUE.


public class Solution {
    public boolean isPalindrome(int x) {
        if(x < 0){
            return false;
        }
        if(x!=0 && x%10==0){
            return false;
        }        
        int half=0;
        while(x>half){
            half=half*10+x%10;
            x=x/10;
        }
        return (x==half||x==half/10);
    }
}
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