Multiply array elements by a number and store result to a new array

pasta_paul

If I have: const arr = [1, 2, 3, 4]; const n = 5; const result = [6, 1, 7, 0]; // 1234 * 5 How do I get result? Edit: First of all, sorry for misleading title. What I try to solve is multiplication of a large number (BigInt not allowed) with some (smaller) integer. So what I try to do is store each digit of large number as a array element and multiply those elements with a multiplier and store result as a new array with each resulting digit as a...

Originally asked by AlexBor on Stack Exchange (stackoverflow) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

You could reduce from the right side by keeping the carry. const array = [1, 2, 3, 4], n = 5, result = array.reduceRight(([c, ...rest], v) => { c += v * n; return [Math.floor(c / 10), c % 10, ...rest]; }, [0]); while (result[0] > 9) { // split carry result.unshift(Math.floor(result[0] / 10)); result[1] %= 10; } while (!result[0] && result.length > 1) result.shift(); // remove leading zeroes console.log(...result);

Full answer by Nina Scholz: https://stackoverflow.stackexchange.com/a/79825823 (CC BY-SA 4.0).

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