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.
1 public class Solution { 2 public bool IsStrobogrammatic(string num) { 3 if (num == null || num.Length == 0) return true; 4 5 int i = 0, j = num.Length - 1; 6 7 while (i <= j) 8 { 9 if ((num[i] == ‘6‘ && num[j] == ‘9‘) || (num[i] == ‘9‘ && num[j] == ‘6‘) || (num[i] == ‘8‘ && num[j] == ‘8‘) || (num[i] == ‘0‘ && num[j] == ‘0‘) || (num[i] == ‘1‘ && num[j] == ‘1‘)) 10 { 11 i++; 12 j--; 13 } 14 else 15 { 16 return false; 17 } 18 } 19 20 return true; 21 } 22 }