# Strobogrammatic Number

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

Write a function to determine if a number is strobogrammatic. The number is represented as a string.

For example, the numbers "69", "88", and "818" are all strobogrammatic.

```
public class Solution {
public boolean isStrobogrammatic(String num) {
if (num == null || num.length() == 0) {
return true;
}
int i = 0, j = num.length() - 1;
while (i <= j) {
char c1 = num.charAt(i), c2 = num.charAt(j);
if (c1 == c2) {
if (c1 != '0' && c1 != '1' && c1 != '8') {
return false;
}
} else {
if (!(c1 == '6' && c2 == '9') && !(c1 == '9' && c2 == '6')) {
return false;
}
}
i++;
j--;
}
return true;
}
}
```

Hope this helps,

Michael