[자료 구조 / Swift] Deque 구현하기

Deque

• 양방향으로 원소 삽입, 삭제가 가능하다.

Deque 구현하기

class Deque<T> {
    var enqueue: [T]
    var dequeue: [T] = []
    
    var isEmpty: Bool { return enqueue.isEmpty && dequeue.isEmpty }
    var count: Int { return enqueue.count + dequeue.count }
    
    init() { enqueue = [T]() }
    init(_ arr: [T]) { enqueue = arr }
    
    func push_front(_ x: T) { dequeue.append(x) }
    func push_back(_ x: T) { enqueue.append(x) }
    func pop_front() -> T? {
        if dequeue.isEmpty {
            dequeue = enqueue.reversed()
            enqueue.removeAll()
        }
        return dequeue.popLast()
    }
    func pop_back() -> T? {
        if enqueue.isEmpty {
            enqueue = dequeue.reversed()
            dequeue.removeAll()
        }
        return enqueue.popLast()
    }
    func front() -> T? {
        if dequeue.isEmpty {
            dequeue = enqueue.reversed()
            enqueue.removeAll()
        }
        return dequeue.last
    }
    func back() -> T? {
        if enqueue.isEmpty {
            enqueue = dequeue.reversed()
            dequeue.removeAll()
        }
        return enqueue.last
    }
    func clear() { enqueue.removeAll(); dequeue.removeAll() }
}