Reverse digits of an integer.

Example1: x = 123, return 321

Example2: x = -123, return -321

Have you thought about this?

Here are some good questions to ask before coding. Bonus points for you if you have already thought through this!

If the integer's last digit is 0, what should the output be? ie, cases such as 10, 100.

Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer, then the reverse of 1000000003 overflows. How should you handle such cases?

Throw an exception? Good, but what if throwing an exception is not an option? You would then have to re-design the function (ie, add an extra parameter).

1 public int reverse(int x) { 2         // Note: The Solution object is instantiated only once and is reused by each test case. 3         boolean positive = (x > 0) ? true : false; 4         int result = 0; 5         x = Math.abs(x); 6         while(x > 0){ 7             result = result * 10 + x % 10; 8             x = x / 10; 9         }10         if(!positive){11             result *= -1;12         }13         return result;14     }

 refactor code：

考虑溢出情况，溢出时result<0，此时返回-1

1 public int reverse(int x) { 2         // Note: The Solution object is instantiated only once and is reused by each test case. 3         boolean positive = (x > 0) ? true : false; 4         int result = 0; 5         x = Math.abs(x); 6         while(x > 0){ 7             result = result * 10 + x % 10; 8             x = x / 10; 9         }10         if(result < 0){11             return -1;12         }13         if(!positive){14             result *= -1;15         }16         return result;17     }