41 lines
1.0 KiB
JavaScript
41 lines
1.0 KiB
JavaScript
// https://www.codewars.com/kata/multiplying-numbers-as-strings/train/javascript
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function multiply(a, b) {
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return a.split('').reduceRight((sum, d, i, arr) => {
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return sumStrings(mul(b, +d) + '0'.repeat(arr.length - i - 1), sum);
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}, '0');
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}
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// mltiple any big int (string) by one digit (0-9)
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function mul(str, d) {
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return d.toString(2).split('').reduceRight((obj, b) => {
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let {res, last} = obj;
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if (b === '1') res = sumStrings(res, last);
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last = sumStrings(last, last);
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return {res, last}
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}, {res: '0', last: str}).res;
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}
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// https://www.codewars.com/kata/sum-strings-as-numbers
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function sumStrings(aa,bb) {
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let a = aa.split('').reverse();
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let b = bb.split('').reverse();
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let c = 0;
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let r = [];
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for (let i = 0; i < Math.max(a.length, b.length); ++i) {
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let sum = (+a[i]|0) + (+b[i]|0) + c;
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if (sum >= 10) {
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r[i] = (sum - 10) + '';
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c = 1;
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} else {
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r[i] = sum + '';
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c = 0;
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}
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}
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if (c) {
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r.push('1');
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}
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return r.reverse().join('').replace(/^0*/, '') || '0';
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}
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