52 lines
1.8 KiB
JavaScript
52 lines
1.8 KiB
JavaScript
const uuid = require('uuid')
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const _ = require('lodash')
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// Custom algorith for two cassettes. For three or more denominations, we'll need
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// to rethink this. Greedy algorithm fails to find *any* solution in some cases.
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// Dynamic programming may be too inefficient for large amounts.
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//
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// We can either require canononical denominations for 3+, or try to expand
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// this algorithm.
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exports.makeChange = function makeChange (cassettes, amount) {
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// Note: Everything here is converted to primitive numbers,
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// since they're all integers, well within JS number range,
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// and this is way more efficient in a tight loop.
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// Another note: While this greedy algorithm possibly works for all major denominations,
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// it still requires a fallback for cases where it might not provide any solution.
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// Example: Denominations: [3, 5, 10] | User inputs 4 times the [3] button, resulting in a 12 fiat tx
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// This algorithm resolves for 1 x [10], and can't resolve the remainder of 2
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const cassetteMap = _.map(cassettes, it => ({
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denomination: it.denomination
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}))
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const amountNum = amount.toNumber()
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const sortedCassettes = _.orderBy(cassetteMap, ['denomination'], ['desc'])
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const finalDist = []
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let mutableAmount = _.clone(amountNum)
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while(mutableAmount >= 0) {
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_.each(sortedCassettes, it => {
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if (mutableAmount === 0) {
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finalDist.push({ provisioned: 0, denomination: it.denomination, id: uuid.v4() })
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return
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}
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const remainder = mutableAmount % it.denomination
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const amountToSub = mutableAmount - remainder
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const numberOfBills = amountToSub / it.denomination
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mutableAmount -= amountToSub
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finalDist.push({ provisioned: numberOfBills, denomination: it.denomination, id: uuid.v4() })
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return
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})
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if (mutableAmount === 0) {
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break
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}
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}
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return finalDist
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}
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