problem split expenses between people algorithm JS

Question

I am making a function that divide expense between people in function what they have paid. But when I split 1€ into 3 people, the return is 0.33 each participant, I want to be [0.33, 0.33, 0.34] How can I make it

I was trying to get the total and view the difference of the result but It doesn't work

score 1 · Accepted Answer · answered Mar 03 '23 at 23:35

1

Work in cents to avoid floating point issues.
Take the floor of dividing the amount by the number of people, then distribute the remainder.

const divide = (amount, n) => [...Array(n)].map((_, i) => 
  Math.floor(amount / n) + (i < amount % n)).reverse();
console.log(divide(100, 3));
console.log(divide(101, 3));

answered Mar 03 '23 at 23:35

Unmitigated

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It returns wrong value when execute `console.log(divide(1, 3))` – Jordy Mar 04 '23 at 00:02
1

@Jordy: [0, 0, 1]? How is that wrong? – Ry- Mar 04 '23 at 00:16
The asker want result be `[0.33, 0.33, 0.34]` – Jordy Mar 04 '23 at 00:20
2

@Jordy I specifically stated "work in cents". $1 = 100 cents... Unless you're saying we can divide 1 cent. – Unmitigated Mar 04 '23 at 00:25
Ok, it makes sense. But the asker ask about `€` instead of `$` – Jordy Mar 04 '23 at 00:28
@Jordy It's the same concept. 1 euro is 100 cents. – Unmitigated Mar 04 '23 at 00:29
This is so useful because later on I can convert the cents to €, THANKS – soap Mar 04 '23 at 09:42

score 1 · Answer 2 · answered Mar 03 '23 at 23:36

You could sum the parts and take for the last the rest of the sum to distribute.

const
    getParts = (value, length) => Array.from(
        { length },
        (s => (_, i) => {
            if (i + 1 === length) return s.toFixed(2);
            const v = (value / length).toFixed(2);
            s -= v;
            return v;            
        })(value)
    );

console.log(getParts(1, 3));

Jordy · Answer 3 · 2023-03-04T00:13:53.523

-1

Let a be the dividend, b be the divisor, and n be the number of decimal places you want. You can try to solve the correct division by looping it. When the last loop comes, you should subtract the total from the cumulative count

let round = (num, n) => {
  return Math.round((num + Number.EPSILON) * Math.pow(10,n)) / Math.pow(10,n);
}

let divide = (a, b, n) => {
  let d = round(a/b, n);
  let res = [];
  for(let i=0; i < b; i++) {
    res.push(i != b-1 ? d : round(a - i*d, n));
  }
  return res;
}
console.log(divide(1,3,2))

edited Mar 04 '23 at 00:13

answered Mar 04 '23 at 00:00

Jordy

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why are we adding `Number.EPSILON` – Ry- Mar 04 '23 at 00:19
According to this [answer](https://stackoverflow.com/a/11832950/12715723), it will round the number correctly. – Jordy Mar 04 '23 at 00:21

problem split expenses between people algorithm JS

3 Answers3