Java Exercises: Check if a number is a strobogrammatic number

Java Basic: Exercise-186 with Solution

Write a Java program to check if a number is a strobogrammatic number. The number is represented as a string.

According to Wikipedia "A strobogrammatic number is a number whose numeral is rotationally symmetric, so that it appears the same when rotated 180 degrees. In other words, the numeral looks the same right-side up and upside down (e.g., 69, 96, 1001). A strobogrammatic prime is a strobogrammatic number that is also a prime number, i.e., a number that is only divisible by one and itself (e.g., 11). It is a type of ambigram, words and numbers that retain their meaning when viewed from a different perspective, such as palindromes."
The first few strobogrammatic numbers are:
0, 1, 8, 11, 69, 88, 96, 101, 111, 181, 609, 619, 689, 808, 818, 888, 906, 916, 986, 1001, 1111, 1691, 1881, 1961, 6009, 6119, 6699, 6889, 6969, 8008, 8118, 8698, 8888, 8968, 9006, 9116, 9696, 9886, 9966, ...

Pictorial Presentation:

Sample Solution:

Java Code:

import java.util.*;
public class Solution {
 public static void main(String[] args) {
  String n = "9006";
  System.out.println("Is " + n + " is Strobogrammatic? " + is_Strobogrammatic(n));
 }

 public static boolean is_Strobogrammatic(String n) {
  if (n == null || n.length() == 0) {
   return true;
  }
  HashMap < Character, Character > map = new HashMap < Character, Character > ();
  map.put('0', '0');
  map.put('1', '1');
  map.put('8', '8');
  map.put('6', '9');
  map.put('9', '6');
  int left = 0;
  int right = n.length() - 1;
  while (left <= right) {
   if (!map.containsKey(n.charAt(right)) || n.charAt(left) != map.get(n.charAt(right))) {
    return false;
   }
   left++;
   right--;
  }
  return true;
 }
}

Sample Output:

Is 9006 is Strobogrammatic? true

Flowchart:

Java Code Editor:

Company:  Google

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