Algs4-1.5.11实现加权quick-find算法

1.5.11实现加权quick-find算法,其中我们总是将较小的分量重命名为较大的分量的标识符。这种改变会对性能产生怎样的影响?
答:每次union需要多访问N次id数组进行判断,同时还需要对两个分量的触点个数的sz赋新值,也会增加数组的访问,性能将会降低。
public class E1d5d11
{
    private int[] id;
    private int[] sz;
    private int count;
    public E1d5d11(int N)
    {
        count=N;
        id=new int[N];
        for (int i=0;i<N;i++)
             id[i]=i;
        //
        sz=new int[N];
        for (int i=0;i<N;i++)
            sz[i]=1;
    }
   
    public int count()
    {return count;}
    
     boolean connected(int p,int q)
     {return find(p)==find(q);}

     public int find(int p)
     {return id[p];}
      
      public  void union(int p,int q)
       {
          int pID=find(p);
          int qID=find(q);
          if (pID==qID) return;
          int totalSize=sz[p]+sz[q];
          int oldID;
          int newID;
          if(sz[p]<sz[q])
            {
              oldID=pID;
              newID=qID;
           }
          else
           {
              oldID=qID;
              newID=pID;
          }
         for (int i=0;i<id.length;i++)
             {
                 if(id[i]==oldID) id[i]=newID;
                 if(id[i]==newID) sz[i]=totalSize;
              }
           count--;
      }
         //

       public static void main(String[] qrgs)
       {
           int N=StdIn.readInt();
           E1d5d11 uf=new E1d5d11(N);
           while (!StdIn.isEmpty())
           {
               int p=StdIn.readInt();
               int q=StdIn.readInt();
               if(uf.connected(p,q)) continue;
               StdOut.println(p+ " " +q);
               uf.union(p,q);
            }//end while
        }//end main
}//end class

posted @ 2018-10-26 10:12  修电脑的龙生  阅读(245)  评论(0编辑  收藏  举报