总额和平均值

本课属于 Coddy Swift 学习旅程的“基础知识”单元。第 81 课，共 86 课。

挑战

简单

在上一课中，你实现了“查看所有支出”功能。现在，为选项 "3" 实现“显示总额和平均值”功能。

修改代码以处理选项 "3"：

用户输入 "3" 时，检查 expenses 数组是否为空
如果数组为空，打印 No expenses to calculate.
如果数组中有支出，计算并显示：
- 所有支出的总额，格式为 Total: $X.X
- 支出的平均值，格式为 Average: $X.X
选项 "4" 仍应打印 Coming soon...
选项 "1"、"2" 和 "5" 应继续像之前一样正常工作

提示：使用 reduce(0, +) 计算总额，并除以 Double(expenses.count) 来计算平均值。

预期行为：

没有支出时输入 "3"，打印 No expenses to calculate.
有支出时输入 "3"，总额打印在一行，平均值打印在下一行

交互示例：

1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
3
No expenses to calculate.
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
1
Enter expense amount:
20.0
Expense added!
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
1
Enter expense amount:
30.0
Expense added!
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
3
Total: $50.0
Average: $25.0
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" {
        print("Coming soon...")
    } else if choice == "4" {
        print("Coming soon...")
    } else if choice == "5" {
        print("Goodbye!")
        break
    } else {
        print("Coming soon...")
    }
}

基础知识中的所有课

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