问题描述： 给定一组日期，将它们按照月份分组并计算每个月的天数。

示例输入：[2019-01-01, 2019-01-02, 2019-02-01, 2019-02-02, 2019-03-01, 2019-12-31]

示例输出：[{month: 1, days: 31}, {month: 2, days: 28}, {month: 3, days: 31}, {month: 12, days: 31}]

使用Kotlin编写代码以按月份分组和计算每个月的天数。

data class Month(val month: Int, var days: Int = 0)

fun groupDaysByMonth(dates: List) : List { val months = mutableMapOf() for (date in dates) { val month = months.getOrPut(date.monthValue) { Month(date.monthValue) } month.days += 1 } return months.values.toList() }

使用示例：

val dates = listOf(LocalDate.of(2019, 1, 1), LocalDate.of(2019, 1, 2), LocalDate.of(2019, 2, 1), LocalDate.of(2019, 2, 2), LocalDate.of(2019, 3, 1), LocalDate.of(2019, 12, 31))

val result = groupDaysByMonth(dates) result.forEach { println(it) }

输出：

Month(month=1, days=2) Month(month=2, days=2) Month(month=3, days=1) Month(month=12, days=1)