_9.java

package com.fishercoder.solutions;

/**
 * Determine whether an integer is a palindrome. Do this without extra space.
 * <p>
 * Some hints:
 * Could negative integers be palindromes? (ie, -1)
 * <p>
 * If you are thinking of converting the integer to string, note the restriction of using extra space.
 * <p>
 * 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?
 * <p>
 * There is a more generic way of solving this problem.
 */
public class _9 {
    
    /**Purely my original solution: just reverse the entire number and compare with itself, return if they two are equal or not.*/
    public boolean isPalindrome(int x) {
        if (x == 0) {
            return true;
        }
        if (x < 0) {
            return false;
        }
        int rev = 0, tmp = x;
        while (tmp != 0) {
            rev *= 10;
            rev += tmp % 10;
            tmp /= 10;
        }
        return rev == x;
    }

    /**Then I turned to Discuss and found a more efficient way: reversing only half and then compare if they're equal.*/

}