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?

For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

Update (2014-11-10):

Test cases had been added to test the overflow behavior.

 

分析：本题理论上很简单，但对溢出的处理需要谨慎。这里本人用了unsigned long来保存reverse结果。

 

1 class Solution { 2 public: 3     int reverse(int x) { 4         bool isNegative = false; 5         if(x<0){ 6             x=-x; 7             isNegative = true; 8         } 9         unsigned long result = 0;10         while(x){11             result = result*10 + x%10;12             x = x/10;13         }14         if(result > INT_MAX) return 0;15         return (isNegative)? int(-result) : int(result) ;16         17     }18 };