scala数据结构和算法-02-用模式匹配实现合并排序

package data

object MergeSortUsePattern {
   def mergeSort[T](compatator:(T,T)=>Boolean)(source:List[T]):List[T]={
    source match{
      case list if (list.length==0)=>return List()
      case list if(list.length==1)=>return list;
      case _=>
    }
    val (left,right)=source.splitAt(source.length/2);
    merge(compatator)(mergeSort(compatator)(left),mergeSort(compatator)(right));
  }
  
  def merge[T](compatator:(T,T)=>Boolean)(left:List[T],right:List[T]):List[T]={
    (left,right)match{
      case (Nil,list)=>return list;
      case (list,Nil)=>return list;
      case (left,right)=>{
        if(compatator(left(0),right(0))){
          return left(0)::merge(compatator)(left.slice(1, left.length),right);
        }else{
          return right(0)::merge(compatator)(left,right.slice(1, right.length))
        }
        
      }
    }
  }
  
  def main(args: Array[String]): Unit = {
    val source=List(1,3,9,8,4,7,5,6)
    println(mergeSort[Int]((x,y)=>{ if (x<y)  true else  false})(source))
  }
}