Reverse Integer (数字反转)

Reverse Integer

Reverse digits of an integer.


Example1: x = 123, return 321

Example2: x = -123, return -321

陷阱

java int 的范围为 -2147483648->214748364710 如果超出则溢出

Code

[code]
public class Solution {
    public int reverse(int x) {
         int flag=1;
            if(x<0){
                flag=-1;
                x=-x;
            }
            int num=0;
            while(x!=0){

                    int temp=x%10;
                    if((Integer.MAX_VALUE-temp)/10<num&&flag==1) //正数时判断是否可能溢出
                        return 0;

                   if((Integer.MIN_VALUE+temp)/-10<num&&flag==-1)
                        return 0; //负数时判断是否溢出
                    num=num*10+temp;

                    x=x/10;
            }

            if(flag==1){

                return num;
            }

            else{

                return -num;
            }
    }
}