Kotlin:将一个列表组合成一张地图

如何使用lambdas将列表分组到地图中?强制性解决方案如下:

private class Data(val a: Int, val b: Int, val c: Int)

@JvmStatic
fun main(args: Array<String>) {
    val dataList = listOf(Data(1, 2, 3), Data(4, 5, 6), Data(7, 8, 9), Data(1, 10, 11))
    val result = mutableMapOf<Int, MutableMap<Int, Int>>()
    for (data in dataList) {
        val aMap = result.getOrPut(data.a) { mutableMapOf() }
        aMap[data.b] = data.c
    }
    println(result)
}