Padovan sequence: Difference between revisions
Added Swift solution
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{{out}}
<pre>
First 20 terms of the Padovan sequence:
1 1 1 2 2 3 4 5 7 9 12 16 21 28 37 49 65 86 114 151
Recurrence and floor functions agree for first 64 terms? true
First 10 strings produced from the L-system:
A B C AB BC CAB ABBC BCCAB CABABBC ABBCBCCAB
Length of first 32 strings produced from the L-system = Padovan sequence? true
</pre>
=={{header|Swift}}==
<lang swift>import Foundation
class PadovanRecurrence: Sequence, IteratorProtocol {
private var p = [1, 1, 1]
private var n = 0
func next() -> Int? {
let pn = n < 3 ? p[n] : p[0] + p[1]
p[0] = p[1]
p[1] = p[2]
p[2] = pn
n += 1
return pn
}
}
class PadovanFloor: Sequence, IteratorProtocol {
private let P = 1.324717957244746025960908854
private let S = 1.0453567932525329623
private var n = 0
func next() -> Int? {
let p = Int(floor(pow(P, Double(n - 1)) / S + 0.5))
n += 1
return p
}
}
class PadovanLSystem: Sequence, IteratorProtocol {
private var str = "A"
func next() -> String? {
let result = str
var next = ""
for ch in str {
switch (ch) {
case "A": next.append("B")
case "B": next.append("C")
default: next.append("AB")
}
}
str = next
return result
}
}
print("First 20 terms of the Padovan sequence:")
for p in PadovanRecurrence().prefix(20) {
print("\(p)", terminator: " ")
}
print()
var b = PadovanRecurrence().prefix(64)
.elementsEqual(PadovanFloor().prefix(64))
print("\nRecurrence and floor functions agree for first 64 terms? \(b)")
print("\nFirst 10 strings produced from the L-system:");
for p in PadovanLSystem().prefix(10) {
print(p, terminator: " ")
}
print()
b = PadovanLSystem().prefix(32).map{$0.count}
.elementsEqual(PadovanRecurrence().prefix(32))
print("\nLength of first 32 strings produced from the L-system = Padovan sequence? \(b)")</lang>
{{out}}
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