kotlin - 什么功能方法可以帮助我实现速度返回算法？

Question

Speedback is the merging of speed-dating with feedback: a 2 min. 1-on-1 talk with all members of a group of people.

I've made a similar question in Computer Science获得有关算法的一些线索，但很难将其转换为函数式编程。

考虑输入:

val team = setOf("alexandre", "sergiu", "joana", "tiago", "susana", "david")

我想做一个循环赛，所有团队成员都必须互相提供反馈。
我想以最大化同时配对数量的方式对人进行分组，以便我们减少总轮数。

所需的输出是:

1st round:
"alexandre" to "sergiu"
"joana" to "tiago"
"susana" to "david"

2nd round:
"alexandre" to "david"
"sergiu" to "tiago"
"susana" to "joana"

3rd round:
...

直到每个人都“约会”每个人。

我有这个:

fun main() {
    val team = setOf("alexandre", "sergiu", "joana", "tiago", "susana", "david")

    println(team.combinations(2))
}

the output so far is the 15 possible pairs (combinations).然后我不确定使用哪种功能方法来获得上面的输出。我看了 groupBy , associateBy , partition但似乎没有一个合适的 - 或者我在 FP 中太新手了。

Answer 1

我刚转了answer你通过计算机科学堆栈交换进入 Kotlin。

fun <T> roundRobin(list: List<T>): List<List<Pair<T, T>>> {
    val n = list.size
    return (if (n % 2.0 == 0.0) roundRobinEven(n) else roundRobinOdd(n)).map { 
        round -> round.map {
            (first, second) -> Pair(list[first], list[second])
        }
    }
}

//For each round (i), (i, n-1) and then Pair((j+i)%(n-1), (n-1−j+i)%(n-1) for the rest
fun roundRobinEven(n: Int): List<List<Pair<Int, Int>>> = 
    List(n-1) { i -> (1..(n/2-1)).map{ j -> Pair((j+i)%(n-1), (n-1-j+i)%(n-1)) }.plusElement(Pair(i, n-1)) }
    
//For each round (i), Pair((j+i)%(n), (n−j+i)%(n)) where 1<=j<=(n-1)/2
fun roundRobinOdd(n: Int): List<List<Pair<Int, Int>>> =
    List(n) { i -> (1..(n-1)/2).map { j -> Pair((j+i)%n, (n-j+i)%n) } }

你可以像这样使用它。里面的每个列表代表一个回合

val team = listOf("alexandre", "sergiu", "joana", "tiago", "susana", "david")
val rounds = roundRobin(team2)
for (round in rounds) {
    println(round)
}

输出:

[(sergiu, susana), (joana, tiago), (alexandre, david)]
[(joana, alexandre), (tiago, susana), (sergiu, david)]
[(tiago, sergiu), (susana, alexandre), (joana, david)]
[(susana, joana), (alexandre, sergiu), (tiago, david)]
[(alexandre, tiago), (sergiu, joana), (susana, david)]

Link to Kotlin playground