迭代器

時間 2019-11-30

標籤迭代简体版

原文原文鏈接

代碼

節點：單鏈表節點LinkNode

鏈表：單鏈表 -->額外方法：getIterator()

public class IteratorLinkList extends List {
    static LinkNode first = null;
    
    public LinkNode getFirst(){
        return first;
    }
    
    public  void setFirst(LinkNode first) {
        IteratorLinkList.first = first;
    }

    public boolean isEmpty() {
        return first==null;
    }
    public void  insertFirst(LinkNode o1) {// 頭插法
        if(isEmpty()) {
            first= o1;
            return;
        }
        o1.next = first;
        first = o1;
    }
     
    // 在指定節點後插入新節點
    public static void insertAfter(LinkNode o1, LinkNode o2) {
        LinkNode current = first;
        LinkNode previous = null;
        while(current!=null){
            if(current.iData == o1.iData && current.dData == o1.dData){
                o2.next = current;
                previous.next = o2;
                return;
            }
            previous = current;
            current = current.next;
        }
        throw new RuntimeException("沒有找到該節點");
    }
    public   LinkNode  deleteFirst() {// 刪除頭節點
        if(isEmpty()) {
            throw new RuntimeException("鏈表爲空沒法進行刪除操做");
        }
        LinkNode temp = first;
        first= first.next; 
        return temp;
    }
    // 顯示鏈表
    public void displayList() {
        LinkNode current = first;
        System.out.println("Display from Front--->End");
        while(current!=null){
            System.out.print(current.iData + "  "+ current.dData+"  ");
            System.out.println();
            current= current.next;
        }
    }
    // 找到指定節點
    public static LinkNode findNode(LinkNode o) {
        LinkNode current = first;
        while(current!=null){
            if(current.iData == o.iData && current.dData == o.dData){
                return current;
            }
            current = current.next;
        }
        throw new RuntimeException("沒有找到該節點");
    }
    // 刪除指定節點
    public void deleteNode(LinkNode o) {
        if(isEmpty()) {
            throw new RuntimeException("鏈表爲空沒法進行刪除操做");
        }
        LinkNode current = first;
        LinkNode previous = null;
        while(current!=null){
            if(current.iData == o.iData && current.dData == o.dData){
                previous.next = current.next;
                return;
            }
            previous = current;
            current = current.next;
        }
        throw new RuntimeException("沒有找到該節點");
    }
       public ListIterator getIterator()  // return iterator
          {
          return new ListIterator(this);  // initialized with
          }  
}

迭代器：

public class ListIterator {
    //current link
    private LinkNode current;
    //previous link
    private LinkNode previous;
    //the  target link list
    private IteratorLinkList ourList;
    
    
    public ListIterator(IteratorLinkList ourList) {
        super();
        this.ourList = ourList;
    }
    //reset the iterator :let it start at first
    public void reset(){
        current = ourList.getFirst();
        previous = null;
    }
    public boolean atEnd(){//whether at the end of target linklist
        return current.next==null;
    }
    public void nextLink() {        // step to next link
        previous = current;
        current = current.next;
    }
    public LinkNode getCurrent()  {     // get current link
        return current;
    }
     public void insertAfter(LinkNode dd){//insert after current link
         if( ourList.isEmpty()) {
             ourList.setFirst(dd);
             reset();
         } 
         dd.next = current.next;
         current.next = dd;
         nextLink();
     }
     public void insertBefore(LinkNode dd){//insert before current link
         if( ourList.isEmpty()) {// the list is empty
             ourList.setFirst(dd);
             reset();
         } if(previous==null){// there is only one item in the list
             ourList.setFirst(dd);
             dd.next = current;
             reset();
         }else{// there is more than one item in the list
            dd.next = current;
            previous.next = dd;
            current = dd;
         }
     }
     public LinkNode deleteCurrent() {   // delete item at current
         LinkNode temp = current;
         if( ourList.isEmpty()) {// the list is empty
             throw new RuntimeException("The List is empty ,could not be deleted any more");
         } if(previous==null){// there is only one item in the list
             ourList.setFirst(null); 
             reset();
         }else{// there is more than one item in the list
            previous.next = current.next;
            if( atEnd() )
                reset();
             else
                current = current.next;
         }
         return temp;
     }
}