grokking_algorithms/06_breadth-first_search/swift/01_breadth-first_search.swift

import Foundation

// As I can see Swift doesn't have Queue default implementation, so we have to use custom on, Degue structure from Swift Algorithm Club
// https://github.com/raywenderlich/swift-algorithm-club/tree/master/Deque
public struct Deque<T> {
    private var array = [T]()
    
    public var isEmpty: Bool {
        return array.isEmpty
    }
    
    public var count: Int {
        return array.count
    }
    
    public mutating func enqueue(_ element: T) {
        array.append(element)
    }
    
    public mutating func enqueueFront(_ element: T) {
        array.insert(element, at: 0)
    }
    
    public mutating func dequeue() -> T? {
        if isEmpty {
            return nil
        } else {
            return array.removeFirst()
        }
    }
    
    public mutating func dequeueBack() -> T? {
        if isEmpty {
            return nil
        } else {
            return array.removeLast()
        }
    }
    
    public func peekFront() -> T? {
        return array.first
    }
    
    public func peekBack() -> T? {
        return array.last
    }
}

func persionIsSeller(name: String) -> Bool {
    return name.characters.last == "m"
}

var graph = [String : [String]]()
graph["you"] = ["alice", "bob", "claire"]
graph["bob"] = ["anuj", "peggy"]
graph["alice"] = ["peggy"]
graph["claire"] = ["thom", "jonny"]
graph["anuj"] = []
graph["peggy"] = []
graph["thom"] = []
graph["jonny"] = []

func search(name: String) -> Bool {
    var searchQueue = Deque<String>()
    //Swift Note: Our custom Deque doesn't have possibility to add new element as array so we have to add elements one by one (insted of +=graph["person"] in the book example)
    for string in graph[name]! {
        searchQueue.enqueue(string)
    }
    // This array is how you keep track of which people you've searched before.
    var searched = [String]()
    while !searchQueue.isEmpty {
        let person = searchQueue.dequeue()
        // Only search this person if you haven't already searched them
        if !searched.contains(person!) {
            if persionIsSeller(name: person!) {
                print("\(person!) is a mango seller!")
                return true
            } else {
                for string in graph[person!]! {
                    searchQueue.enqueue(string)
                }
                // Marks this person as searched
                searched.append(person!)
            }
        }
    }
    
    return false
}

if search(name: "you") == false {
    print("Mango seller Not Found!")
} // => thom is a mango seller!