Prime triangle: Difference between revisions
Added Swift solution
(Added Java solution) |
(Added Swift solution) |
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Elapsed time: 754 milliseconds
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=={{header|Swift}}==
<lang swift>import Foundation
func isPrime(_ n: Int) -> Bool {
guard n > 0 && n < 64 else {
return false
}
return ((UInt64(1) << n) & 0x28208a20a08a28ac) != 0
}
func primeTriangleRow(_ a: inout ArraySlice<Int>) -> Bool {
let start = a.startIndex
let end = a.endIndex
if a.count == 2 {
return isPrime(a[start] + a[start + 1])
}
for i in start + 1..<end - 1 {
if isPrime(a[start] + a[i]) {
a.swapAt(i, start + 1)
if primeTriangleRow(&a[start + 1..<end]) {
return true
}
a.swapAt(i, start + 1)
}
}
return false
}
func primeTriangleCount(_ a: inout ArraySlice<Int>) -> Int {
let start = a.startIndex
let end = a.endIndex
var count = 0
if a.count == 2 {
if isPrime(a[start] + a[start + 1]) {
count += 1
}
} else {
for i in start + 1..<end - 1 {
if isPrime(a[start] + a[i]) {
a.swapAt(i, start + 1)
count += primeTriangleCount(&a[start + 1..<end])
a.swapAt(i, start + 1)
}
}
}
return count
}
func printRow(_ a: [Int]) {
if a.count == 0 {
return
}
print(String(format: "%2d", a[0]), terminator: "")
for x in a[1...] {
print(String(format: " %2d", x), terminator: "")
}
print()
}
for n in 2...20 {
var a = Array(1...n)
if primeTriangleRow(&a[...]) {
printRow(a)
}
}
print()
for n in 2...20 {
var a = Array(1...n)
if n > 2 {
print(" ", terminator: "")
}
print("\(primeTriangleCount(&a[...]))", terminator: "")
}
print()</lang>
{{out}}
<pre>
1 2
1 2 3
1 2 3 4
1 4 3 2 5
1 4 3 2 5 6
1 4 3 2 5 6 7
1 2 3 4 7 6 5 8
1 2 3 4 7 6 5 8 9
1 2 3 4 7 6 5 8 9 10
1 2 3 4 7 10 9 8 5 6 11
1 2 3 4 7 10 9 8 5 6 11 12
1 2 3 4 7 6 5 12 11 8 9 10 13
1 2 3 4 7 6 13 10 9 8 11 12 5 14
1 2 3 4 7 6 13 10 9 8 11 12 5 14 15
1 2 3 4 7 6 5 12 11 8 15 14 9 10 13 16
1 2 3 4 7 6 5 12 11 8 9 10 13 16 15 14 17
1 2 3 4 7 6 5 8 9 10 13 16 15 14 17 12 11 18
1 2 3 4 7 6 5 8 9 10 13 16 15 14 17 12 11 18 19
1 2 3 4 7 6 5 8 9 10 13 16 15 14 17 12 19 18 11 20
1 1 1 1 1 2 4 7 24 80 216 648 1304 3392 13808 59448 155464 480728 1588162
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