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.
Example 1:
Input: "69"
Output: true
Example 2:
Input: "88"
Output: true
Example 3:
Input: "962"
Output: false
public boolean isStrobogrammatic(String num) {
HashMap<Character, Character> map = new HashMap<>();
map.put('6','9');
map.put('9','6');
map.put('0','0');
map.put('1','1');
map.put('8','8');
int l = 0, r = num.length()-1;
while(l <= r) {
if(!map.containsKey(num.charAt(l)) ||map.get(num.charAt(l)) != num.charAt(r))
return false;
l++;
r--;
}
return true;
}