leetcode — palindrome-number

import org.lep.leetcode.parseint.IntegerParser;

/**
* Source : https://oj.leetcode.com/problems/palindrome-number/ *
* Created by lverpeng on 2017/7/5.
*
* Determine whether an integer is a palindrome. Do this without extra space.
*
* 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.
*
*/
public class IntPalindrome {

/**
* 负数可以自己决定是否进行判断，这里不进行判断，归为不是
* 依次取出整数的第一位和最后一位比较
* 第一位：整除
* 最后一位：对10求余
*
* @param num
* @return
*/
public boolean isPalindrome (int num) {
if (num < 0) {
return false;
}
int base = 1;
while (num / (base) >= 10) {
base *= 10;
}

while (num != 0) {
int left = num / base;
int right = num % 10;
if (left != right) {
return false;
}
num = (num % base) / 10;
base /= 100;
}
return true;
}

public static void main(String[] args) {
IntPalindrome palindrome = new IntPalindrome();
System.out.println(palindrome.isPalindrome(0));
System.out.println(palindrome.isPalindrome(-101));
System.out.println(palindrome.isPalindrome(1001));
System.out.println(palindrome.isPalindrome(1234321));
System.out.println(palindrome.isPalindrome(2147447412));
System.out.println(palindrome.isPalindrome(5155));
System.out.println(palindrome.isPalindrome(5552));
}
}