Palindrome Number(lintcode 491)

Description

Check a positive number is a palindrome or not.

A palindrome number is that if you reverse the whole number you will get exactly the same number.

Notice:
It's guaranteed the input number is a 32-bit integer, but after reversion, the number may exceed the 32-bit integer.

Example

11, 121, 1, 12321 are palindrome numbers.

23, 32, 1232 are not palindrome numbers.

Interface

public class Solution {
    /**
     * @param num a positive number
     * @return true if it's a palindrome or false
     */
    public boolean palindromeNumber(int num) {
        // Write your code here

    }
}

Idea

Two ways. Treat num as a number or treat num as a string.

Solution

public class Solution {
    /**
     * @param num a positive number
     * @return true if it's a palindrome or false
     */
    public boolean palindromeNumber(int num) {
        // treat num as a string
        String str = Integer.toString(num);
        int i = 0;
        while (i < str.length() / 2) {
            if (str.charAt(i) != str.charAt(str.length() - 1 - i)) {
                break;
            }
            ++i;
        }

        return i == str.length() / 2;
    }
}

public class Solution {
    /**
     * @param num a positive number
     * @return true if it's a palindrome or false
     */
    public boolean palindromeNumber(int num) {
        // treat num as a number
        int temp = num;
        int rev = 0;
        while (temp != 0) {
            rev = rev * 10 + temp % 10;
            temp = temp / 10;
        }
        return rev == num;
    }
}