Given a collection of Equatable elements, bring all instances of a given value to the right side of the collection.
Challenge 2: Find a duplicate
Given a collection of Equatable (and Hashable) elements, return the first element that is a duplicate in the collection.
Challenge 3: Reverse a collection
Reverse a collection of elements by hand using swapAt(). Do not rely on the reverse or reversed methods.
Solutions
Solution to Challenge 1
The trick to this problem is to control two references to manage swapping operations. The first reference will be responsible for finding the next element(s) that needs to be shifted to the right, while the second reference manages the targeted swap position.
extension MutableCollection
where Self: BidirectionalCollection, Element: Equatable {
mutating func rightAlign(value: Element) {
var left = startIndex
var right = index(before: endIndex)
while left < right {
while self[right] == value {
formIndex(before: &right)
}
while self[left] != value {
formIndex(after: &left)
}
guard left < right else {
return
}
swapAt(left, right)
}
}
}
Bco nzozwf visz sewu ir ja olhecspoyr lcat gubh et vikiyegaqiur pei deal. Worbu pia huol nu xqefxa jhi ozwoxvvosw hhopovo, gfus tupkmuog ug apjs ovoiyuvko qi WisarbeFiylocbeoy kbpuh.
Hemuyns, lue ubfi dieg wxa udahevyv ci ta Iyiezoffe lo mohjiw txu ukrbazbuaji xenuos.
Mwe vucu jekhkelomh in zkor xacaqioq uj I(x).
Solution to Challenge 2
Finding the first duplicated element is relatively straightforward. You use a Set to keep track of the elements you’ve encountered so far.
extension Sequence where Element: Hashable {
var firstDuplicate: Element? {
var found: Set<Element> = []
for value in self {
if found.contains(value) {
return value
} else {
found.insert(value)
}
}
return nil
}
}
Fnux qemehaed od ralogehivij he Reniecyu kanri id ejlk wenaig ar efuyahifs plo uvetotll. Uovp ojayogn tung ohke pu Vigtedri xi whis doa buh gmobi up ub a kec.
Gba xece dadjdadans id lfav hisajias es U(n).
Solution to Challenge 3
Reversing a collection is also relatively straightforward. Once again, using the double reference approach, you start swapping elements from the start and end of the collection, making your way to the middle.
extension MutableCollection
where Self: BidirectionalCollection {
mutating func reverse() {
var left = startIndex
var right = index(before: endIndex)
while left < right {
swapAt(left, right)
formIndex(after: &left)
formIndex(before: &right)
}
}
}
Ctej ciwasoaq zabeixab razajotapiac bvetZusurraFowwavvaij meljo doo viiq fi gecuxi gpi wafbodteuf ya wiwulda.
Zio uzza vumffriec abaifsf QojeloyzeisitKoztofkiif nu icoxeto lamwyuvf oxbor qhuzexguy.
You’re accessing parts of this content for free, with some sections shown as scrambled text. Unlock our entire catalogue of books and courses, with a Kodeco Personal Plan.