I want to implement a function to check if a given number do contain les than two different digits, that are called duodigits

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 and 0 and 2 are three different digits

How may I implement a method , which may iterate and check if it's a duodgits or not and return true or false as result

I want to implement a function to check if a given number do contain les than two different digits, that are called duodigits

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 and 0 and 2 are three different digits

How may I implement a method , which may iterate and check if it's a duodgits or not and return true or false as result

• javascript

• Make a Set whose elements are all the digits in the number. Then get the size of the set. – Barmar Commented Mar 25, 2022 at 22:20
• new Set(Math.abs(num).toString().split("")).length > 2 – 2pichar Commented Mar 25, 2022 at 22:24
• @2pichar A Set doesn’t have a length. You mean size. – Sebastian Simon Commented Mar 25, 2022 at 22:27
• @2pichar, note that you don't need the split because JS already considers strings to be arrays of characters ^_^ – Ben Commented Mar 25, 2022 at 22:56

3 Answers 3

Here is how I would do it:

/**
 * Checks if a number is a duodigit.
 * @param {number} num 
 * @returns {boolean}
 */
function isDuodigit(num) {
  return new Set(Math.abs(num).toString()).size <= 2;
}

my solution would be:

function isDuoDigit(num) {

  const numArr = Array.from(num.toString());

  const uniqueNums = numArr.filter((num, index) => numArr.indexOf(num) === index);

  return uniqueNums.length > 2 ? "Number is not DuoDigit" : "Number is DuoDigit!"
}

console.log(isDuoDigit(11111000000)); // Number is DuoDigit!
console.log(isDuoDigit(111155555500000)); // Number is NOT DuoDigit!

1. Convert a number to an array of strings ( 102 = ["1", "0", "2"] )

   const numArr = Array.from(num.toString());

2. Get an array with unique values (without duplicates)

   const uniqueNums = numArr.filter((num, index) => numArr.indexOf(num) === index);

3. We check if length of uniqueNums array is more then 2. If it's true, it means number is NOT DuoDigit and if length of array 2 or less, number is DuoDigit

   return uniqueNums.length > 2 ? "Number is not DuoDigit" : "Number is DuoDigit!"

If you want to do it without a set or string conversion.

function isDuoDigit(num){
    num = Math.abs(num);
    let first = '', second = '';
      while (num > 0) {
        let digit = num % 10;
        if(first === '')
          first = digit
        else if(second === '')
          second = digit
        else if(first !== digit && second !== digit)
           return false;
        num = Math.trunc(num / 10);
      }
  return true;
}