```
class Solution {
public:
bool isStrobogrammatic(string num) {
int size = num.size();
int n = (size%2 == 0 ? size/2 : size/2+1);
for(int i = 0;i < n;i++){
if(num[i] == '2' || num[i] == '3' || num[i] == '4' || num[i] == '5' || num[i] == '7')
return false;
if(num[i] == '6' && num[size-i-1] != '9')
return false;
if(num[i] == '9' && num[size-i-1] != '6')
return false;
if((num[i] != '6' && num[i] !='9') && num[i] != num[size-1-i])
return false;
}
return true;
}
};
```

This is a special case of palindrome.We need only think about 6 and 9.