BFS implementation.

Algorithms/Searching/BFS.playground/Contents.swift

@@ -1 +1,49 @@
 /// BFS algorithm implementation.
+
+class Node {
+    var name: String
+    var children: [Node]
+
+    init(name: String) {
+        self.name = name
+        children = []
+    }
+
+    // Use `Set` to track previously visited nodes.
+    var bfsVisited = Set<String>()
+
+    func addChild(name: String) -> Node {
+        let childNode = Node(name: name)
+        children.append(childNode)
+
+        return self
+    }
+
+    func breadthFirstSearch(array: inout [String]) -> [String] {
+        bfsQueueTraversal(node: self, array: &array)
+        return array
+    }
+
+    /// BFS traversal using `queue`.
+    private func bfsQueueTraversal(node: Node, array: inout [String]) {
+        var fakeQueue = [Node]()
+        fakeQueue.append(node) // Init with node passed in
+
+        while !fakeQueue.isEmpty {
+            let currentNode = fakeQueue.removeFirst()
+
+            // Skip previously visited node
+            if bfsVisited.contains(currentNode.name) { continue }
+
+            // Mark as visited
+            bfsVisited.insert(currentNode.name)
+            // Update array
+            array.append(currentNode.name)
+
+            // Use queue to process child nodes
+            for childNode in currentNode.children {
+                fakeQueue.append(childNode)
+            }
+        }
+    }
+}