스택[BOJ]

스택

  import Foundation


  struct Stack1 {
      private var list: [Int] = []

      mutating func push(_ value: Int) {
          list.append(value)
      } 

      mutating func pop() -> Int{
          if list.isEmpty {
              return -1
          }
          return list.removeLast()
      }

      func size() -> Int {
          return list.count
      }

      func empty() -> Int {
          return list.isEmpty ? 1 : 0
      }

      func top() -> Int {
          return list.last ?? -1
      }
  }

  var stack = Stack1()

  for _ in 0..<Int(readLine()!)! {
      let command = readLine()!.split(separator: " ")

      switch command[0] {
      case "push":
          stack.push(Int(command[1])!)
      case "pop":
          print(stack.pop())
      case "size":
          print(stack.size())
      case "empty":
          print(stack.empty())
      case "top":
          print(stack.top())
      default:
          break
      }
  }

시간복잡도 O(n)