Data commit

Task/Van-Eck-sequence/Swift/van-eck-sequence.swift

@@ -0,0 +1,29 @@
+struct VanEckSequence: Sequence, IteratorProtocol {
+    private var index = 0
+    private var lastTerm = 0
+    private var lastPos = Dictionary<Int, Int>()
+
+    mutating func next() -> Int? {
+        let result = lastTerm
+        var nextTerm = 0
+        if let v = lastPos[lastTerm] {
+            nextTerm = index - v
+        }
+        lastPos[lastTerm] = index
+        lastTerm = nextTerm
+        index += 1
+        return result
+    }
+}
+
+let seq = VanEckSequence().prefix(1000)
+
+print("First 10 terms of the Van Eck sequence:")
+for n in seq.prefix(10) {
+    print(n, terminator: " ")
+}
+print("\nTerms 991 to 1000 of the Van Eck sequence:")
+for n in seq.dropFirst(990) {
+    print(n, terminator: " ")
+}
+print()