有没有一种方法可以在Kotlin中使用Initializator函数构造HashSet? [英] Is there a way to construct a HashSet with initializator function in Kotlin?

问题描述

要从 Facebook黑客杯2016年 Boomerang Constellations问题中的文件中读取星星，可以定义以下扩展功能:

To read Stars from a file in the Facebook Hacker Cup's 2016 Boomerang Constelations problem, following extension function can be defined:

fun BufferedReader.readStars(n: Int): Set<Star> {
    return Array(n) {
        val (l1, l2) = readLine().split(" ").map { it.toInt() }
        Star(l1, l2)
    }.toHashSet()
}

代码紧凑，但是首先将值读入数组，然后转换为HashSet.有没有办法直接用Kotlin初始化大小为n的HashSet和Initializator函数?

Code is compact but the values are first read into an array and then converted to a HashSet. Is there a way to directly initialize a HashSet with the size of n and initializator function in Kotlin?

更新:标准Kotlin库中是否存在现有方式?

UPDATE: Is there an existing way in standard Kotlin libs?

推荐答案

您始终可以使用apply就地初始化对象:

You can always use apply to initialize objects in-place:

HashSet<Star>(n).apply {
    repeat(n) {
        val (l1, l2) = readLine()!!.split(' ').map { it.toInt() }
        put(Star(l1, l2))
    }
}

如果每次输入都不太方便，请编写扩展功能:

If that's too inconvenient too type every time, write an extension function:

inline fun <T> createHashSet(n : Int, crossinline fn: (Int) -> T) = HashSet<T>(n).apply {
    repeat(n) { add(fn(it)) }
}

用法:

createHashSet<Star>(n) {
    val (l1, l2) = readLine()!!.split(' ').map { it.toInt() }
    Star(l1, l2)
}

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