LeetCode 7: Reverse Integer

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 store integers within the 32-bit signed integer range: $[-2^{31},2^{31}-1]$. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

class Solution {
    public int reverse(int x) {
        if(x == 0)return 0;
        int rev = 0;
        if(x > 0) {
			while(x > 0) {
                if(rev >= 0x7fffffff/10.0)return 0;
				rev = rev*10 + x%10;
				x = x/10;         
			}		
        }else {
			while(x < 0) {
                if(rev < 0x80000000/10.0)return 0;
				rev = rev*10 + x%10;
				x = x/10;         
			}		
        }
        return rev;     
    }
}

关键点：

• int 类型
  最大值为： 0x7fffffff，即常见的 2147483647
  最小值为：0x80000000，即 -2147483648
• 数值问题
  考虑边界情况非常重要