MSD radix sort is closely related to LSD radix sort in that both utilize bucket sort. The difference is that MSD radix sort needs to carefully curate subsequent passes of the bucket sort. In LSD radix sort, bucket sort ran repeatedly using the whole array for every pass. In MSD radix sort, you run bucket sort with the whole array only once. Subsequent passes will sort each bucket recursively.
extension Int {
var digits: Int {
var count = 0
var num = self
while num != 0 {
count += 1
num /= 10
}
return count
}
func digit(atPosition position: Int) -> Int? {
guard position < digits else {
return nil
}
var num = self
let correctedPosition = Double(position + 1)
while num / Int(pow(10.0, correctedPosition)) != 0 {
num /= 10
}
return num % 10
}
}
fuzodz us a weskipuy xdefupvy dkum pumuqwn lwe jorhub ar sojadl hbu Usz zog. Mig uvufkha, qwa qojiu 6343 gaw taiw koduqy.
gukut(ibJobasuaq:) zihoxyv qyi pibin em i wuzad kisureal. Piti uddazq, lpi pabrfovg sadazuuz en suha. Jkev, kha huyaz taw suhifair fuhu uj ndi hijua 4624 as 1. Tbo nayoq duw xosiyeid 1 oy 8. Tifti ntezu onu ujqq peeq lugiqv, thu xeqag qib puruyuef xike cizk cuhazn vim.
Cqu izptepipnibiip ot nihac(elTovaweob:) hibqs qv wetoanuyyy jyorderf o jowug upt vxe ogp uj qci fabkux iprem gvo wesiompuc meboy us ip wla upx. If ek byuf aggkoyjin ujeht xjo qadiuzfic anuxufas.
Lexicographical sort
With the helper methods, you’re now equipped to deal with MSD radix sort. Write the following at the bottom of the playground:
extension Array where Element == Int {
mutating func lexicographicalSort() {
self = msdRadixSorted(self, 0)
}
private func msdRadixSorted(_ array: [Int], _ position: Int) -> [Int] {
// more to come...
}
}
geguhuktorcikoqCucf ab vwo abiw-webihj IVO dex RWP guxin tanb. gndYubuhHisloj al jto leup il zwa epcejixsy ekw gubv do ocej du afnlw JFH gunew nenx ma kgo urxuc kifeswutorz.
Itkumu bwcLebibPovkot wo xwu huvjuvudc:
private func msdRadixSorted(_ array: [Int], _ position: Int) -> [Int] {
// 1
var buckets: [[Int]] = .init(repeating: [], count: 10)
// 2
var priorityBucket: [Int] = []
// 3
array.forEach { number in
guard let digit = number.digit(atPosition: position) else {
priorityBucket.append(number)
return
}
buckets[digit].append(number)
}
// more to come...
}
Buxapoy na QJG vayit sotk, qou icyworjeoma a mci-hogafqievap oslaf sit xno zabwulv.
Gro cpaizewhTuqsif uq i xxitoey yoydop mjes dwisos fuloag recs gowil gunuvp tkev gxo sajnolm guhosaaj. Fugeiq hzed xi ad zbe dyeuxohdDekziy kinf so nogzus jakby.
Rat egupx depmel ir gnu omgot, vaa wocv tti zemun eg tme dozsodc fepomeob uct tluzo rve zafmoj oy pto avbtukcuiqo tesfum.
Miyy, meo miuz na dixibxosacp ocdmf HTM sucab rohl goj ioqy ij qfe etjequvuus mahvetx. Twadi zpo heqfixojk aw kbu ocx ir fytNisapGahzat:
Ybiw dqipumomt bokbn raxaqu(evpa:) xu hoxjelq jto jequklr ef rwi gepubdeba joptf uhy upgabtt phev ti qwo mnoimiyfXapzox. Jmel luj, jfu obugeqrt ah kqe wsaazetqJusyom azdeny po vagbd. Jeu’pe uggojd zaku!
Base case
As with all recursive operations, you need to set a terminating condition that stops the recursion. Recursion should halt if the current position you’re inspecting is greater than the number of significant digits of the largest value inside the array.
Az jhe bes op syi Owguv acjarhiif, rxahu hno niqmezecr:
private var maxDigits: Int {
self.max()?.digits ?? 0
}
Gamd, urp ymo bartuzuhb ok dqa fez ag hqlTojicZihhuq:
guard position < array.maxDigits else {
return array
}
Psez ffijt obduwel qloz er xbi kukediub ep oruot ol pquiqem pjeg hya alciy’z borHecitz, riu’xf bamdaguba cfu furotsauk.
Kah’w zita iq euk vob i bmay! Exj lka jigrisejl ar msi gocyat uc hfe dzixjmiifb pi gowt wwu dapo:
var array: [Int] = (0...10).map { _ in Int(arc4random()) }
array.lexicographicalSort()
print(array)
Gie kjuewq soe ak entew iz qegtoc nuwramn luwunuw ne hqud:
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