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本课属于 Coddy Swift 学习旅程的“基础知识”单元。第 82 课，共 86 课。

挑战

简单

在上一课中，你实现了“Show total and average”功能。现在，为选项 "4" 实现“Clear all expenses”功能。

修改代码以处理选项 "4"：

当用户输入 "4" 时，从 expenses 数组中移除所有元素
清空数组后，打印 All expenses cleared!
其他所有选项（"1"、"2"、"3" 和 "5"）都应继续像之前一样工作

提示：使用 removeAll() 方法清除所有数组元素。

预期行为：

输入 "4" 时，清空 expenses 数组并显示确认消息
清空后查看支出时，应显示 No expenses recorded.
清空后显示总额和平均值时，应显示 No expenses to calculate.

交互示例：

1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
1
Enter expense amount:
15.0
Expense added!
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
1
Enter expense amount:
25.0
Expense added!
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
2
Your expenses:
- $15.0
- $25.0
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
4
All expenses cleared!
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
2
No expenses recorded.
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
5
Goodbye!

亲手试试

// Daily Expense Tracker - Menu Display

var expenses: [Double] = []

while true {
    // TODO: Write your code below to print the menu options
    // Each option should be on its own line with the format: "number. option text"
    print("1. Add expense")
    print("2. View all expenses")
    print("3. Show total and average")
    print("4. Clear all expenses")
    print("5. Exit")
    
    let choice = readLine()
    
    if choice == "1" {
        print("Enter expense amount:")
        if let input = readLine(), let amount = Double(input) {
            expenses.append(amount)
            print("Expense added!")
        }
    } else if choice == "2" {
        if expenses.isEmpty {
            print("No expenses recorded.")
        } else {
            print("Your expenses:")
            for expense in expenses {
                print("- $\(expense)")
            }
        }
    } else if choice == "3" {
        if expenses.isEmpty {
            print("No expenses to calculate.")
        } else {
            let total = expenses.reduce(0, +)
            let average = total / Double(expenses.count)
            print("Total: $\(total)")
            print("Average: $\(average)")
        }
    } else if choice == "4" {
        print("Coming soon...")
    } else if choice == "5" {
        print("Goodbye!")
        break
    } else {
        print("Coming soon...")
    }
}

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