Modify the result of problem
P10
in such a way that if an element has no duplicates it is simply copied into the result list. Only elements with duplicates are transferred as
(N, E)
terms.
Example:
scala> encodeModified(List('a, 'a, 'a, 'a, 'b, 'c, 'c, 'a, 'a, 'd, 'e, 'e, 'e, 'e)) res0: List[Any] = List((4,'a), 'b, (2,'c), (2,'a), 'd, (4,'e))
spanList通过递归将列表拆分成多个元素相同的列表,(takes,lefts)=curList span(_==curList.head) 根据条件将列表分成两部分
//11 def encodeModified[A](ls: List[A]) = { def spanList[A](curList:List[A]):List[List[A]]={ if(curList.isEmpty) List(List()) else{ val list=Nil val (takes,lefts)=curList span(_==curList.head) if(lefts==Nil) List(takes) else List(takes):::spanList(lefts) } } spanList(ls).map(e=> if(e.length>1){(e.length,e.head)} else{e.head} ) } def main(args: Array[String])= { println(encodeModified(List(1,1,2,2,3,4,4,5,7))) }
结果
List((2,1), (2,2), 3, (2,4), 5, 7)
参考答案