7. Reverse Integer
class Solution {
public:
int reverse(int x) {
int flag=x<0?-1:1;
x=abs(x);
int ten=10;
long res=0; //long！！不能用int
while(x>0){
int num=x%ten;
x=x/ten;
res = res*10+num;
}
res=res*flag;
return (res<INT_MIN || res>INT_MAX) ? 0 : res;
}
};
