i am trying to solve a problem about duodigit concept in java.

Here it is:

We call duodigit an integer whose decimal representation does not use more than two different digits.

For example :

• 12 , 110 , -33333 : are all duodigits , since they have no more than two different digits
• 102 : is not a duodigit since his digits 1 , 0 and 2 are three different digits.

Implement the isDuoDigit(number) method which returns a string:

• y if number is a duodigit
• n otherwise

EXAMPLE:

public class Solution {

    public static String isDuoDigit(int number){
        /* Write your code here */

    return "";
    }
}

So i came up with this solution:

public class Solution_duoDigit {

    public static String isDuoDigit(int number) {
        /* Write your code here */
        Set<Integer> set= new HashSet<>();
        set.add(number);
        if(set.size()<=2){
            return "y";
        }else{
            return "n";
        }
        
    }

    public static void main(String[] args) {

        System.out.println(Solution_duoDigit.isDuoDigit(12));
        System.out.println(Solution_duoDigit.isDuoDigit(110));
        System.out.println(Solution_duoDigit.isDuoDigit(102));
        System.out.println(Solution_duoDigit.isDuoDigit(-2021));

    }
}

But my solution is not complete and doesn't work because I do not know how to express the fact that it does not have more than two different digits in java code. Can you help me please?

CodePudding user response：

You can use .chars():

public static String isDuoDigit(int number) {
    boolean isDuoDigit = Integer.toString(number).replace("-", "").chars().distinct().count() <= 2;
    return isDuoDigit ? "y" : "n";
}

Alternatively you can do:

public static String isDuoDigit(int number) {
    boolean isDuoDigit = Integer.toString(Math.abs(number)).chars().distinct().count() <= 2;
    return isDuoDigit ? "y" : "n";
}

Then:

System.out.println(isDuoDigit(12));
System.out.println(isDuoDigit(110));
System.out.println(isDuoDigit(-3333));
System.out.println(isDuoDigit(102));

Output:

y
y
y
n

CodePudding user response：

Well, using a Set is not a bad idea, as it eliminates the duplicates.

The problem with your current code is that you add the whole integer to the set, which results in the set having just a single value.

What you need to do, is adding each digit separately to the set.

You need to do a few things:

• Remove any sign, as this obviously does not count as digit;
• Get each digit separately;
• For each digit, add it to the set;
• Get the size of the set.

String s = Integer.toString(Math.abs(number));
Set<Character> set = new HashSet<>();
for (int i = 0; i < s.length(); i  ) {
    char c = s.charAt(i);
    set.add(c);
}
return (set.size() <= 2 ? "y" : "n");

Note: I could have used Java Streams instead, but I'm not sure if you're accustomed to them yet. Here's a one-liner using streams:

return Integer.toString(Math.abs(number)).chars().distinct().count() <= 2 ? "y" : "n";

But that's indeed pretty much what Oboe already said in his answer.

CodePudding user response：

and also you can use the below,

        int i = -3333;
        String s = String.valueOf(i).replace("-", "");
        Map<Integer, Integer> map = new HashMap<>();
        for (int j = 0; j < s.length(); j  ) {
            map.merge((int) s.charAt(j), 1, Integer::sum);
        }
        long count = map.values()
                        .size();
        System.out.println(count > 2 ? "true" : "false");