Leetcode 7 Reverse Integer

Reverse digits of an integer.

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

Solution 1: Positive/Negative formula is same. Need the positive flag just to deal with the overflow.

 public class Solution {  
   public int reverse(int x) {  
     boolean positive=true;  
     if (x<0) positive=false;  
     int res=0;  
     while (x!=0) {  
       int num=x%10;  
       //to make sure result will not overflow, when overflow return 0  
       if (positive && res>(Integer.MAX_VALUE-num)/10) return 0;  
       if (!positive && res<(Integer.MIN_VALUE-num)/10) return 0;  
       res=res*10+num;  
       x/=10;  
     }  
     return res;  
   }  
 }  

Solution 2: if can use long in the code, will be much cleaner.

 public class Solution {  
   public int reverse(int x) {  
     long res=0;  
     while (x!=0) {  
       res=res*10+x%10;  
       if (res>Integer.MAX_VALUE || res<Integer.MIN_VALUE) return 0;  
       x/=10;  
     }  
     return (int)res;  
   }  
 }