CS 61B homewok8

  public static LinkedQueue mergeSortedQueues(LinkedQueue q1, LinkedQueue q2) {
    // Replace the following line with your solution.
      LinkedQueue mergedQueue = new LinkedQueue();
      int flag = 0;
      Object q1item=0;
      Object q2item=0;
      try{
          while((!q1.isEmpty())&&(!q2.isEmpty())||((q1item!=null)&&(q2item!=null)&&flag==1)){
              
              if(flag==0){q1item = q1.dequeue();q2item = q2.dequeue();}
              flag=1;
              while(((Comparable)(q1item)).compareTo(((Comparable)(q2item)))>=0){
                  mergedQueue.enqueue(q2item);
                  if(!q2.isEmpty()){q2item=q2.dequeue();}else{q2item=null;break;}
              }
              while(q2item!=null&&((Comparable)(q1item)).compareTo(((Comparable)(q2item)))<0){
                  mergedQueue.enqueue(q1item);
                  if(!q1.isEmpty()){q1item=q1.dequeue();}else{q1item=null;break;}
              }
          }
          if(flag==1){    //万一q1 q2是空的
          if(q1item!=null){mergedQueue.enqueue(q1item);}
          if(q2item!=null){mergedQueue.enqueue(q2item);}}
          if(!q2.isEmpty()){
              mergedQueue.append(q2);              
          }else if(!q1.isEmpty()){
              mergedQueue.append(q1);
          }
                                   
      }catch(QueueEmptyException e){ System.err.println("Error:  attempt to dequeue from empty queue.");}
    return mergedQueue;
  }

  public static LinkedQueue makeQueueOfQueues(LinkedQueue q) {
    // Replace the following line with your solution.
      LinkedQueue QueueOfQueues = new LinkedQueue();
      try{
      while(!q.isEmpty()){
          Object OneQueue = q.dequeue();
          LinkedQueue OneLinkedqueue = new LinkedQueue();
          OneLinkedqueue.enqueue(OneQueue);
          QueueOfQueues.enqueue(OneLinkedqueue);
      }
      }catch(QueueEmptyException e){ System.err.println("Error:  attempt to dequeue from empty queue.");}
    return QueueOfQueues;
  }

  public static void mergeSort(LinkedQueue q) {
    // Your solution here.
      LinkedQueue Queues = makeQueueOfQueues(q);
      try{
      while(Queues.size()>1){
          Queues.enqueue(mergeSortedQueues((LinkedQueue)Queues.dequeue(),(LinkedQueue)Queues.dequeue()));
      }
      }catch(QueueEmptyException e){ System.err.println("Error:  attempt to dequeue from empty queue.");}
      q.append(Queues);
  }

 public static void quickSort(LinkedQueue q) {
    // Your solution here.
      if(!q.isEmpty()){
          int pivotnum = 1+(int)(Math.random()*q.size());
          Comparable pivot = (Comparable)q.nth(pivotnum);
          LinkedQueue qSmall = new LinkedQueue();
          LinkedQueue qLarge = new LinkedQueue();
          LinkedQueue qEquals= new LinkedQueue();
          partition(q,pivot,qSmall,qEquals,qLarge);
          if(!qSmall.isEmpty()){
          quickSort(qSmall);}
          if(!qLarge.isEmpty()){
          quickSort(qLarge);}
          q.append(qSmall);
          q.append(qEquals);
          q.append(qLarge);
      }    
            
  }

  public static void partition(LinkedQueue qIn, Comparable pivot, 
                               LinkedQueue qSmall, LinkedQueue qEquals, 
                               LinkedQueue qLarge) {
    // Your solution here.
      try{
      while(!qIn.isEmpty()){
          Object Item = qIn.dequeue();
          if(((Comparable)(Item)).compareTo(pivot)>0){
              qLarge.enqueue(Item);
          }else if(((Comparable)(Item)).compareTo(pivot)<0){
              qSmall.enqueue(Item);
          }else{
              qEquals.enqueue(Item);
          }
      }
      }catch(QueueEmptyException e){ System.err.println("Error:  attempt to dequeue from empty queue.");}
  }