swiftPractice[24]_迴圈練習（下）

nested loop 巢狀迴圈進階練習

基本的原理花了一兩週，通了之後進階練習只要 2 小時！🤩🤩

單排變化

✦ 用 i == 1 控制第一排變化。

  count = 5
  icon = ""
  
  for i in 1...count{
      for _ in 1...count{
          if i == 1{
              icon += "🐼"
          }else{
              icon += "🌕"
          }
      }
      icon += "\n"
  }
  textLabel.text = icon

左對角線

✦ 熊貓出現位置跟當前排數一樣，所以用 i == j 控制熊貓。

  count = 5
  icon = ""
  for i in 1...count{
      for j in 1...count{
          if i == j{
              icon += "🐼"
          }else{
              icon += "🌕"
          }
      }
      icon += "\n"
  }
  textLabel.text = icon

右對角線

✦ 熊貓出現位置跟排數相反，而且是遞減，設定變數 panda 等於總排數，然後在外圈的 loop 控制每次跑完 panda-1。

  count = 5
  icon = ""
  var panda = count
  for i in 1...count{
      for j in 1...count{
          if j == panda{
              icon += "🐼"
          }else{
              icon += "🌕"
          }
      }
      panda -= 1
      icon += "\n"
  }
  textLabel.text = icon

叉叉

✦ 把前兩個做法合併！

  count = 5
  icon = ""
  var panda = count
   for i in 1...count{
       for j in 1...count{
           if j == panda || i == j{
              icon += "🐼"
         }else{
            icon += "🌕"
          }
      }
      panda -= 1
      icon += "\n"
  }
  textLabel.text = icon

十字

✦ 總排數是奇數時，先宣告變數計算正中間是第幾排，橫向用外圈 loop 控制，縱向用內圈 loop 控制。

  count = 5
  icon = ""
  var middle = (count+1)/2
  for i in 1...count{
      for j in 1...count{
          if j == middle || i == middle{
              icon += "🐼"
          }else{
              icon += "🌕"
          }
      }
      icon += "\n"
  }
  textLabel.text = icon

外框

✦ 橫向與縱向的最後一排都是 count，橫向用外圈 loop 控制，縱向用內圈 loop 控制。

  count = 5
  icon = ""

  for i in 1...count{
      for j in 1...count{
          if i == 1 || i == count{
              icon += "🐼"
          }else if j == 1 || j == count{
              icon += "🐼"
          }else{
              icon += "🌕"
          }
      }
      icon += "\n"
  }
  textLabel.text = icon

交錯

✦ 一開始思考的時候非常土法煉鋼，先分成雙數排跟單數排，再分開判斷單一排的雙數、單數位置的 icon 如下。後來看了答案發現大前輩 peter 的作法更精簡聰明！！

//我的作法
  count = 5
  icon = ""
  
  for i in 1...count{
      for j in 1...count{
          if i % 2 == 0{
              if j % 2 == 0{
                  icon += "🐼"
              }else{
                  icon += "🌕"
              }
          }else{
              if j % 2 == 0{
                  icon += "🌕"
              }else{
                  icon += "🐼"
              }
          }
      }
      icon += "\n"
  }
  textLabel.text = icon

//大前輩作法
var content = ""
let count = 5
for i in 1...count {
    for j in 1...count {
        if (i + j) % 2 == 0 {
            content += "👧🏻"
        } else {
            content += "👦🏽"
        }
    }
    content += "\n"
}

每排不同 icon

✦ 做一個 array 裝各種 icon，橫向由外圈 loop 控制，由於第一排要對應到第一個 array成員，所以代表外圍排數位置的 i 要減 1。

  count = 5
  icon = ""
  var icons = ["🐭","🐮","🐯","🐰","🐲"]
  for i in 1...count{
      for _ in 1...count{
      icon += icons[i-1]
      }
      icon += "\n"
  }
  textLabel.text = icon

作業出處

#60 畫星星蘋果