breadthFirstSearch.Swift

class Node: Hashable {
  var adjacentNodes = [Node]() 
}

func breadthFirstSearch(from startingNode: Node{
  let queue = [startingNode] 
  var visited = Set<Node>()
  
  while let next = queue.first { 
    visited.insert(next)
    queue.remove(at: 0)
    
    next.adjacentNodes.forEach({
      if visited.contains($0) == false {
        queue.append($0)
      }
    })
  }
}