迴圈控制 Loop Statement

標籤

• for 迴圈
• while 迴圈
• 巢狀迴圈

for 迴圈

• 基本架構

  for (值) in (陣列) {
      (執行的動作)
  }
  

• 數字

  for i in 1...5 {
      print("\(i) ", terminator: "")
  }
  

  • 輸出結果

    1 2 3 4 5
    

• 陣列

  for i in ["a", "b", "c", "d"] {
      print("\(i) ", terminator: "")
  }
  

  • 輸出結果

    a b c d
    

• 字典

  let dictionary = [1: "John", 2: "Harry", 3: "Kevin", 4: "Alex"]
  for(i, j) in dictionary {
      print("\(i): \(j) ", terminator: "")
  }
  

  • 輸出結果

    2: Harry 3: Kevin 1: John 4: Alex
    

• 純循環（不取值 ）

  for _ in 1...5 {
      print("GOOD ", terminator: "")
  }
  

  • 輸出結果

    GOOD GOOD GOOD GOOD GOOD
    

• 純循環（加入運算子 ）

  var data = 0, data2 = 50
  for _ in 1...5 {
      data += data2
  } 
  print(data)
  

  • 輸出結果

    250
    

• 隨機取值

  var number: UInt32
  for _ in 1...5 {
      number = arc4random_uniform(100)
      print("\(number) ", terminator: "")
  }
  

  • 輸出結果

    47 40 25 6 53
    

    • 附註：number 取值需放於迴圈中才能執行五次動作，否則如下。

      65 65 65 65 65
      

while 迴圈

• 基本架構

  while (條件) {
      (條件滿足，執行的動作)
  }
  

  var data = 0, data2 = 50
  while data == 0 {
      data = data2
  } 
  print(data)
  

  • 輸出結果

    50
    

• 運算（從50 加回0 ）

  var data = 0, data2 = 50
  while data2 >= 0 {
      data += data2
      data2 -= 1
  }
  print(data)
  

  • 輸出結果

    1275
    

    • 附註：data2 的位子決定結果是 50 ＋...＋ 0，或是 49 ＋...＋ 2。

• repeat while

  repeat {
      (條件滿足，執行的動作)
  } while (條件)
  

  var data = 0, data2 = 50
  repeat {
      data = data2
  } while data == 0
  print(data)
  

  • 輸出結果

    50
    

巢狀迴圈

• for 迴圈 & for 迴圈

  for i in 1...5 {
      print("\(i) ", terminator: "")
      for j in 1...5 {
          print("\(j)", terminator: "")
      }
      print("")
  }
  

  • 輸出結果

    1 12345
    2 12345
    3 12345
    4 12345
    5 12345
    

• for 迴圈 & while 迴圈

  for i in 1...5 {
      var j: Int = 0
      while j <= i {
          print("\(j)", terminator: "")
          j += 1
      }
      print("")
  }
  

  • 輸出結果

    01
    012
    0123
    01234
    012345
    

• 巢狀迴圈 ＆ 運算子

  for i in 1...3 {
      for j in 1...3 {
          print("\(i) + \(j) = \(i + j) ", terminator: "")
      }
      print("")
  }
  

  • 輸出結果

    0 + 0 = 0 0 + 1 = 1 0 + 2 = 2 0 + 3 = 3
    1 + 0 = 1 1 + 1 = 2 1 + 2 = 3 1 + 3 = 4
    2 + 0 = 2 2 + 1 = 3 2 + 2 = 4 2 + 3 = 5
    3 + 0 = 3 3 + 1 = 4 3 + 2 = 5 3 + 3 = 6