Sample of BinaryTree with BFS navigation

BinaryTree-BFS.swift

import Cocoa
indirect enum BinaryTree<T> {
    case node(BinaryTree, T, BinaryTree)
    case empty
}

extension BinaryTree {
    
    static func leaf(_ value: T) -> BinaryTree {
        return .node(.empty,value,.empty)
    }
    
    func bfs(execute: (T) -> Void) {
        bfs(node: self, execute: execute)
    }
    
    private func bfs(node: BinaryTree<T>, execute: (T) -> Void) {
        var queue = [BinaryTree]()
        queue.append(node)
        while(queue.count > 0) {
            let first = queue.removeFirst()
            switch first {
            case .node(let left, let value, let right):
                queue.append(left)
                queue.append(right)
                execute(value)
                break
            default:
                continue
            }
        }
    }
}
let tree: BinaryTree<Int> = .node(.node(.leaf(2),5,.leaf(7)),10,.node(.leaf(11),15,.leaf(30)))
tree.bfs { value in
    print(value)
}
/*********************************
 Output:
 10
 5
 15
 2
 7
 11
 30
 *********************************/