How to get minimal possible combination of 4 digit number

Question

I have 4 digit integer number. I have to get the minimal number which is a combination of those original numbers (can't start with zeros)

function changeDigitsOrder(num){
 return Number(num.toString().split('').sort().join(''))
}

It works for numbers that doesn't have 0, but how can I get 1005 from 1500

So you need to yank out the zeros and append that after the smallest non zero — epascarello, Feb 03 '21 at 18:43

score 3 · Answer 1 · answered Feb 03 '21 at 18:45

3

You could switch zeros and the following value.

function changeDigitsOrder(num) {
    return +num
        .toString()
        .split('')
        .sort((a, b) => a - b)
        .join('')
        .replace(/(0+)(.)/, '$2$1');
}

console.log(changeDigitsOrder(1500)); // 1005
console.log(changeDigitsOrder(321));  //  123

answered Feb 03 '21 at 18:45

Nina Scholz

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Thank you, can you please briefly explain what .replace(/(0+)(.)/, '$2$1'); does? – BernaraD Feb 03 '21 at 20:10
it searches for zeroes and a non zero following character and takes both groups in different order. – Nina Scholz Feb 03 '21 at 20:28

score 0 · Answer 2 · answered Feb 03 '21 at 19:10

I played with destructuring and lookbehind

const re = /(0{0,})+([1-9]{0,})+/g;
const smallest = num => {
  let str = num.toString().split('').sort().join('')
  let [parts] = str.matchAll(re)
  let [_, zeroes, other] = parts
  return +(other.replace(/(?<=^.{1})/, zeroes))
};

console.log(smallest(1500))
console.log(smallest(1245))
console.log(smallest(5421))
console.log(smallest(421))

How to get minimal possible combination of 4 digit number

2 Answers2