Data commit

Task/Stern-Brocot-sequence/Swift/stern-brocot-sequence.swift

@@ -0,0 +1,40 @@
+struct SternBrocot: Sequence, IteratorProtocol {
+  private var seq = [1, 1]
+
+  mutating func next() -> Int? {
+    seq += [seq[0] + seq[1], seq[1]]
+
+    return seq.removeFirst()
+  }
+}
+
+func gcd<T: BinaryInteger>(_ a: T, _ b: T) -> T {
+  guard a != 0 else {
+    return b
+  }
+
+  return a < b ? gcd(b % a, a) : gcd(a % b, b)
+}
+
+print("First 15: \(Array(SternBrocot().prefix(15)))")
+
+var found = Set<Int>()
+
+for (i, val) in SternBrocot().enumerated() {
+  switch val {
+  case 1...10 where !found.contains(val), 100 where !found.contains(val):
+    print("First \(val) at \(i + 1)")
+    found.insert(val)
+  case _:
+    continue
+  }
+
+  if found.count == 11 {
+    break
+  }
+}
+
+let firstThousand = SternBrocot().prefix(1000)
+let gcdIsOne = zip(firstThousand, firstThousand.dropFirst()).allSatisfy({ gcd($0.0, $0.1) == 1 })
+
+print("GCDs of all two consecutive members are \(gcdIsOne ? "" : "not")one")