Bell numbers: Difference between revisions

=={{header|Swift}}==

{{trans|Kotlin}}

<lang swift>public struct BellTriangle<T: BinaryInteger> {

@usableFromInline

var arr: [T]

@inlinable

public internal(set) subscript(row row: Int, col col: Int) -> T {

get { arr[row * (row - 1) / 2 + col] }

set { arr[row * (row - 1) / 2 + col] = newValue }

}

@inlinable

public init(n: Int) {

arr = Array(repeating: 0, count: n * (n + 1) / 2)

self[row: 1, col: 0] = 1

for i in 2...n {

self[row: i, col: 0] = self[row: i - 1, col: i - 2]

for j in 1..<i {

self[row: i, col: j] = self[row: i, col: j - 1] + self[row: i - 1, col: j - 1]

}

}

}

}

let tri = BellTriangle<Int>(n: 15)

print("First 15 Bell numbers:")

for i in 1...15 {

print("\(i): \(tri[row: i, col: 0])")

}

for i in 1...10 {

print(tri[row: i, col: 0], terminator: "")

for j in 1..<i {

print(", \(tri[row: i, col: j])", terminator: "")

}

print()

}</lang>

{{out}}

<pre>First 15 Bell numbers:

1: 1

2: 1

3: 2

4: 5

5: 15

6: 52

7: 203

8: 877

9: 4140

10: 21147

11: 115975

12: 678570

13: 4213597

14: 27644437

15: 190899322

1

1, 2

2, 3, 5

5, 7, 10, 15

15, 20, 27, 37, 52

52, 67, 87, 114, 151, 203

203, 255, 322, 409, 523, 674, 877

877, 1080, 1335, 1657, 2066, 2589, 3263, 4140

4140, 5017, 6097, 7432, 9089, 11155, 13744, 17007, 21147

21147, 25287, 30304, 36401, 43833, 52922, 64077, 77821, 94828, 115975</pre>