总额与平均值

本课属于 Coddy Kotlin 学习旅程的“基础知识”单元。第 88 课，共 93 课。

挑战

中等

在上一课中，你实现了“View All Expenses”功能。现在，为选项 3 实现“Total and Average”功能。

修改程序以处理选项 3：

如果 expenses 列表为空，则输出 No expenses recorded.
如果有费用，则计算并输出：
- Total: $X，其中 X 是所有费用的总和
- Average: $Y，其中 Y 是所有费用的平均值

其他选项应继续像之前一样运行：

选项 1：添加费用
选项 2：查看所有费用
选项 5：输出 Goodbye! 并退出
选项 4 或无效选项：输出 Invalid option

输入格式：

以字符串形式提供菜单选项和费用金额。

输出格式：

输出菜单，然后根据每个操作输出相应的响应。

示例：

如果输入为 3、1、20.0、1、30.0、1、10.0、3 和 5，输出应为：

--- Expense Tracker ---
1. Add Expense
2. View All Expenses
3. Total and Average
4. Clear All
5. Exit
Choose an option:
No expenses recorded.
--- Expense Tracker ---
1. Add Expense
2. View All Expenses
3. Total and Average
4. Clear All
5. Exit
Choose an option:
Enter expense amount:
Expense added!
--- Expense Tracker ---
1. Add Expense
2. View All Expenses
3. Total and Average
4. Clear All
5. Exit
Choose an option:
Enter expense amount:
Expense added!
--- Expense Tracker ---
1. Add Expense
2. View All Expenses
3. Total and Average
4. Clear All
5. Exit
Choose an option:
Enter expense amount:
Expense added!
--- Expense Tracker ---
1. Add Expense
2. View All Expenses
3. Total and Average
4. Clear All
5. Exit
Choose an option:
Total: $60.0
Average: $20.0
--- Expense Tracker ---
1. Add Expense
2. View All Expenses
3. Total and Average
4. Clear All
5. Exit
Choose an option:
Goodbye!

亲手试试

fun main() {
    val expenses = mutableListOf<Double>()
    
    while (true) {
        println("--- Expense Tracker ---")
        println("1. Add Expense")
        println("2. View All Expenses")
        println("3. Total and Average")
        println("4. Clear All")
        println("5. Exit")
        println("Choose an option:")
        
        val choice = readLine()
        
        if (choice == "1") {
            println("Enter expense amount:")
            val amount = readLine()!!.toDouble()
            expenses.add(amount)
            println("Expense added!")
        } else if (choice == "2") {
            if (expenses.isEmpty()) {
                println("No expenses recorded.")
            } else {
                println("Your expenses:")
                for (expense in expenses) {
                    println("- \$$expense")
                }
            }
        } else if (choice == "5") {
            println("Goodbye!")
            break
        } else {
            println("Invalid option")
        }
    }
}

基础知识中的所有课

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