package list
/**
* 对List进行高效的排序和倒排序
* @author zhangyun
*/
object ListTest {
def main(args: Array[String]) {
def mergesort[T](less: (T,T) => Boolean) (input: List[T]): List[T] = {
/*
* @param xList 要合并的有序集合
* @param yList 要合并的有序集合
* @return 合并后的集合
*/
def merge(xList: List[T], yList: List[T]): List[T] = {
(xList, yList) match {
case(Nil,_) => yList
case(_,Nil) => xList
case(x :: xtail, y :: ytail) =>
if (less(x,y)) x :: merge(xtail, yList)
else y :: merge(xList, ytail)
}
}
val n = input.length / 2 // 将输入集合拆分为两个子集合
if (n ==0) input
else {
val (x,y) = input splitAt n
merge(mergesort(less)(x),mergesort(less)(y))
}
}
println(mergesort((x: Int, y: Int) => x < y)(List(2,28,1,35,22)))
val reversed_mergedsort=mergesort((x: Int, y: Int) => x > y) _
println(reversed_mergedsort(List(2,28,1,35,22)))
}
}
执行输出结果为：
List(1, 2, 22, 28, 35)
List(35, 28, 22, 2, 1)
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