Reverse Integer - 反转一个int，溢出时返回0

Reverse Integer

Reverse digits of an integer.

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

若反转的数溢出，直接返回0

可以用计算结果来判断溢出，也可以用因数来判断

Java代码实现：

 public class ReverseInteger {
     public static int reverseInt(int x){
         if (x == 0) {
             return 0;
         }
         int flag = -1;
         int result = 0;
         if (x < 0) {
             x = x * flag;
             if (x < 0) {
                 return 0;
             }
         } else {
             flag = 1;
         }
         int digits = 1;
         int temp = x;
         while(temp/10 != 0){
             digits++;
             temp/=10;
         }
         //judge before calculate at every may out of range place
         for (int i = 1; i <= digits; i++) {
             int a,b;
             a = (int) (x/Math.pow(10, i-1));
             a = a%10;//get the single number
             b = (int) Math.pow(10, digits-i);
             if ((a*b<0) || (a > 2 && (digits - i) == 9)) {//use number to judge
                 return 0;
             } else {
                 temp = a*b;
             }
             if (result + temp < 0) {//judge
                 return 0;
             } else {
                 result += temp;
             }
         }
         return result*flag;
     }
     public static void main(String args[]){
         int max = 2147483647;
         int min = -2147483648;
         System.out.println(reverseInt(0));
         System.out.println(reverseInt(1534236469));
         System.out.println(reverseInt(-2133847412));
     }
 }

输出：

0
0
-2147483312