2.9 KiB
id | title | challengeType | forumTopicId | dashedName |
---|---|---|---|---|
5e4ce2a1ac708cc68c1df25d | Long multiplication | 1 | 385269 | long-multiplication |
--description--
Explicitly implement long multiplication.
This is one possible approach to arbitrary-precision integer algebra.
--instructions--
Write a function that takes two strings of large numbers as parameters. Your function should return the product of these two large numbers as a string.
Note: In JavaScript, arithmetic operations are inaccurate with large numbers, so you will have to implement precise multiplication yourself.
--hints--
mult
should be a function.
assert(typeof mult == 'function');
mult("18446744073709551616", "18446744073709551616")
should return a string.
assert(typeof mult('18446744073709551616', '18446744073709551616') == 'string');
mult("18446744073709551616", "18446744073709551616")
should return "340282366920938463463374607431768211456"
.
assert.equal(
mult('18446744073709551616', '18446744073709551616'),
'340282366920938463463374607431768211456'
);
mult("31844674073709551616", "1844674407309551616")
should return "58743055272886011737990786529368211456"
.
assert.equal(
mult('31844674073709551616', '1844674407309551616'),
'58743055272886011737990786529368211456'
);
mult("1846744073709551616", "44844644073709551616")
should return "82816580680737279241781007431768211456"
.
assert.equal(
mult('1846744073709551616', '44844644073709551616'),
'82816580680737279241781007431768211456'
);
mult("1844674407370951616", "1844674407709551616")
should return "3402823669833978308014392742590611456"
.
assert.equal(
mult('1844674407370951616', '1844674407709551616'),
'3402823669833978308014392742590611456'
);
mult("2844674407370951616", "1844674407370955616")
should return "5247498076580334548376218009219475456"
.
assert.equal(
mult('2844674407370951616', '1844674407370955616'),
'5247498076580334548376218009219475456'
);
--seed--
--seed-contents--
function mult(strNum1, strNum2) {
}
--solutions--
function mult(strNum1, strNum2) {
var a1 = strNum1.split("").reverse();
var a2 = strNum2.toString().split("").reverse();
var aResult = new Array;
for ( var iterNum1 = 0; iterNum1 < a1.length; iterNum1++ ) {
for ( var iterNum2 = 0; iterNum2 < a2.length; iterNum2++ ) {
var idxIter = iterNum1 + iterNum2; // Get the current array position.
aResult[idxIter] = a1[iterNum1] * a2[iterNum2] + ( idxIter >= aResult.length ? 0 : aResult[idxIter] );
if ( aResult[idxIter] > 9 ) { // Carrying
aResult[idxIter + 1] = Math.floor( aResult[idxIter] / 10 ) + ( idxIter + 1 >= aResult.length ? 0 : aResult[idxIter + 1] );
aResult[idxIter] %= 10;
}
}
}
return aResult.reverse().join("");
}