作業#29 — 畫星星蘋果 — nested loop(巢狀迴圈) 練習

目的: 學習使用 for 迴圈。

作業來源：

#60 畫星星蘋果

基本題

1. 畫 2 種 Apple，比方有紅色跟綠色。

範例

A. 底線

    @IBAction func changeApple(_ sender: UISlider) {
        var content = ""
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"


        for i in 1...row {
            if i <= row-1 {
                for _ in 1...row {
                    content.append("🍎")
                }
            } else {
                for _ in 1...row {
                    content.append("🍏")
                }
            }
            content.append("\n")
        }
        appleLabel.text = content
    }

B. 對角線

    @IBAction func changeApple(_ sender: UISlider) {
        var content = ""
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"


        for i in 1...row {
                for j in 1...row {
                    if i != j {
                    content.append("🍎")
                } else {
                    content.append("🍏")
                }
            }
            content.append("\n")
        }
        appleLabel.text = content
    }

C. 棋盤格

    @IBAction func changeApple(_ sender: UISlider) {
        var content = ""
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"


        for i in 1...row {
                for j in 1...row {
                    if (i+j) % 2 == 0 {
                    content.append("🍎")
                } else {
                    content.append("🍏")
                }
            }
            content.append("\n")
        }
        appleLabel.text = content
    }

進階題

1. 從 segmented control 選擇形狀，有正方形，三角形，金字塔和菱形四種。
2. 從 slider 改變數量。

A. 正方形

範例

    @IBAction func changeApple(_ sender: UISlider) {
        
        var content = ""
        
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"
        for _ in 1...row {
            for _ in 1...row {
                content += "🍎"
            }
            content += "\n"
        }
        appleLabel.text = content
    }

B. 三角形

範例

    @IBAction func changeApple(_ sender: UISlider) {
        var content = ""
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"
        for i in 1...row {
            for _ in 1 ... i {
                content += "🍎"
            }
            content += "\n"
        }
        appleLabel.text = content
    }

C. 金字塔

範例

    @IBAction func changeApple(_ sender: UISlider) {
        var content = ""
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"
        for i in 1...row {
                // 避免  lowerBound > upperBound
                if row > i {
                    for _ in 1...(row-i) {
                        content += "🥝"
                    }
                }
                    for _ in 1 ... 2*i-1 {
                        content += "🍎"
                    }
            content += "\n"
        }
        appleLabel.text = content
    }

＊參考 Peter 的解答後，發現 //避免 lowerBound > upperBound 這一段更好的寫法是使用 ..< ：

//我原本的答案：
if row > i {
      for _ in 1...(row-i) {
          content += "🥝"
      }
  }

//Peter 的解答：
for _ in i..<count {
        content += "🥝"
    }

D. 菱形

範例

    @IBAction func changeApple(_ sender: UISlider) {
        var content = ""
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"
        for i in 1...2*row-1 {
                // 避免  lowerBound > upperBound
            if row > i {
                for _ in 1...(row-i) {
                        content += "🥝"
                }
            } else if i > row {
                for _ in 1...(i-row) {
                    content += "🥝"
                }
            }
            
            if i <= row {
                for _ in 1 ... 2*i-1 {
                    content += "🍎"
                }
            } else {
                for _ in 1 ... (2*(2*row-i)-1) {
                    content += "🍎"
                }
            }
            content += "\n"
        }
        appleLabel.text = content
    }

＊同參考 Peter 的解答後，發現更好的寫法可以先假設兩個變數 奇異果總數及 app蘋果總數，兩個分別的變動為 遞減1/遞增1 及 遞增2/遞減2 ：

//Peter 的解答：
var content = ""
let count = 5
var greenCount = count - 1
var appleCount = 1
for i in 1...count*2-1 {
    for _ in 0..<greenCount {
        content += "🍏"
    }
    for _ in 1...appleCount {
        content += "🍎"
    }
    if i < count {
        greenCount -= 1
        appleCount += 2
    } else {
        greenCount += 1
        appleCount -= 2
    }
   
    content += "\n"
}

E. 每排顯示不同圖案，搭配 array。

範例

a. 三角形

    let emoji = ["","🧛‍♀️","👻","🎅","🧙‍♀️","🦸‍♀️"]
    
    @IBAction func changeApple(_ sender: UISlider) {
        var content = ""
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"


        for i in 1...row {
            for _ in 1...i {
                content.append(emoji[i])
            }
            content.append("\n")
        }
        appleLabel.text = content
    }

b. 正方形

    let emoji = ["","🧛‍♀️","👻","🎅","🧙‍♀️","🦸‍♀️"]
    
    @IBAction func changeApple(_ sender: UISlider) {
        var content = ""
        sender.value = sender.value.rounded()
        let row = Int(sender.value)
        numberLabel.text = "\(row)"


        for i in 1...row {
            for _ in 1...row {
                content.append(emoji[i])
            }
            content.append("\n")
        }
        appleLabel.text = content
    }