7. Reverse Integer

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

Overflow!!!

  public int reverse(int x) {  
     if(x == Integer.MIN_VALUE) return 0;  
     int sign = 1;  
     if(x < 0){  
       sign = -1;  
       x = -x;  
     }  
     int ans = 0;  
     while(x != 0){  
       int d = x%10;  
       if(ans <= (Integer.MAX_VALUE - d)/10)  
         ans = ans * 10 + d;  
       else  
         return 0;  
       x/=10;  
     }  
     return sign*ans;  
   }