leetcode -- Reverse Integer

Reverse Integer

Description

Given a 32-bit signed integer, reverse digits of an integer.

• Example 1:

Input: 123
Output:  321

• Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:

Assume we are dealing with an environment which could only hold integers within the 32-bit signed integer range. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

public int reverse ( int x ) {
        if (x >= 0 && x <= 9){
            return x;
        }
        boolean flag = true;
        if (x < 0){
            flag = false;
            x = - x;
        }
        long resultInt=0;
        while( x > 0 ) {
            int y = x % 10;
            x = x / 10;
            resultInt = resultInt * 10 + y;
        }

        int answer = ( resultInt > Integer.MAX_VALUE || resultInt < Integer.MIN_VALUE ) ? 0 : (int) resultInt;
        if ( flag == true ) {
            return answer;
        } else {
            return (-1) * answer;
        }
    }

here, we need be careful for answer whether it is bigger than Integer.MAX_VALUE (32 bit int value) or smaller than Integer.MIN_VALUE (32 bit int value).