Data commit

Task/Hash-join/Swift/hash-join.swift

@@ -0,0 +1,42 @@
+func hashJoin<A, B, K: Hashable>(_ first: [(K, A)], _ second: [(K, B)]) -> [(A, K, B)] {
+  var map = [K: [B]]()
+
+  for (key, val) in second {
+    map[key, default: []].append(val)
+  }
+
+  var res = [(A, K, B)]()
+
+  for (key, val) in first {
+    guard let vals = map[key] else {
+      continue
+    }
+
+    res += vals.map({ (val, key, $0) })
+  }
+
+  return res
+}
+
+let t1 = [
+  ("Jonah", 27),
+  ("Alan", 18),
+  ("Glory", 28),
+  ("Popeye", 18),
+  ("Alan", 28)
+]
+
+let t2 = [
+  ("Jonah", "Whales"),
+  ("Jonah", "Spiders"),
+  ("Alan", "Ghosts"),
+  ("Alan", "Zombies"),
+  ("Glory", "Buffy")
+]
+
+print("Age | Character Name | Nemesis")
+print("----|----------------|--------")
+
+for (age, name, nemesis) in hashJoin(t1, t2) {
+  print("\(age) | \(name) | \(nemesis)")
+}