PART I:
DList:
1 public DList() { 2 // Your solution here. Similar to Homework 4, but now you need to specify 3 // the `list' field (second parameter) as well. 4 head = newNode(null, null, null, null); 5 head.prev =head; 6 head.next =head; 7 size = 0; 8 } 9 10 /** 11 * insertFront() inserts an item at the front of this DList. 12 * 13 * @param item is the item to be inserted. 14 * 15 * Performance: runs in O(1) time. 16 **/ 17 public void insertFront(Object item) { 18 // Your solution here. Similar to Homework 4, but now you need to specify 19 // the `list' field (second parameter) as well. 20 head.next = newNode(item, this, head, head.next); 21 head.next.next.prev = head.next; 22 size++; 23 } 24 25 /** 26 * insertBack() inserts an item at the back of this DList. 27 * 28 * @param item is the item to be inserted. 29 * 30 * Performance: runs in O(1) time. 31 **/ 32 public void insertBack(Object item) { 33 // Your solution here. Similar to Homework 4, but now you need to specify 34 // the `list' field (second parameter) as well. 35 head.prev = newNode(item, this, head.prev, head); 36 head.prev.prev.next = head.prev; 37 size++; 38 } 39 DListNode: 40 public void insertAfter(Object item) throws InvalidNodeException { 41 if (!isValidNode()) { 42 throw new InvalidNodeException("insertAfter() called on invalid node"); 43 } 44 // Your solution here. Will look something like your Homework 4 solution, 45 // but changes are necessary. For instance, there is no need to check if 46 // "this" is null. Remember that this node's "myList" field tells you 47 // what DList it's in. You should use myList.newNode() to create the 48 // new node. 49 DListNode newNode=new DListNode(item, (DList)this.myList, this, this.next); 50 this.next.prev=newNode; 51 this.next=newNode; 52 this.myList.size++; 53 } 54 55 /** 56 * insertBefore() inserts an item immediately preceding this node. If this 57 * node is invalid, throws an exception. 58 * 59 * @param item the item to be inserted. 60 * @exception InvalidNodeException if this node is not valid. 61 * 62 * Performance: runs in O(1) time. 63 */ 64 public void insertBefore(Object item) throws InvalidNodeException { 65 if (!isValidNode()) { 66 throw new InvalidNodeException("insertBefore() called on invalid node"); 67 } 68 // Your solution here. Will look something like your Homework 4 solution, 69 // but changes are necessary. For instance, there is no need to check if 70 // "this" is null. Remember that this node's "myList" field tells you 71 // what DList it's in. You should use myList.newNode() to create the 72 // new node. 73 DListNode newNode=new DListNode(item,(DList)this.myList,this.prev,this); 74 this.prev.next = newNode; 75 this.prev=newNode; 76 this.myList.size++; 77 } 78 79 /** 80 * remove() removes this node from its DList. If this node is invalid, 81 * throws an exception. 82 * 83 * @exception InvalidNodeException if this node is not valid. 84 * 85 * Performance: runs in O(1) time. 86 */ 87 public void remove() throws InvalidNodeException { 88 if (!isValidNode()) { 89 throw new InvalidNodeException("remove() called on invalid node"); 90 } 91 // Your solution here. Will look something like your Homework 4 solution, 92 // but changes are necessary. For instance, there is no need to check if 93 // "this" is null. Remember that this node's "myList" field tells you 94 // what DList it's in. 95 this.prev.next=this.next; 96 this.next.prev=this.prev; 97 this.myList.size--; 98 99 // Make this node an invalid node, so it cannot be used to corrupt myList. 100 myList = null; 101 // Set other references to null to improve garbage collection. 102 next = null; 103 prev = null; 104 }
结果无误，太长了所以不贴了hhh
PART II:
- insert主要就是遍历list，然后找出合适的位置插入。一般情况下使用前插即可，遍历到list末端时可以使用后插。
- union比较两个list，由于都是sorted list所以也是从前往后遍历即可。通常情况下也是使用前向插入。注意遍历到末尾的情况。
- intersect操作方法类似，需要注意sList的长度问题，SList到达末端后需要依次删除curNode的内容。还有就是remove node的方式，之前使用curNode = curNode.next();
curNode.prev().remove(); 这样在最后一个node的情况不太好处理，于是更改了一下
1 /** 2 * insert() inserts a Comparable element into this Set. 3 * 4 * Sets are maintained in sorted order. The ordering is specified by the 5 * compareTo() method of the java.lang.Comparable interface. 6 * 7 * Performance: runs in O(this.cardinality()) time. 8 **/ 9 public void insert(Comparable c) { 10 try { 11 if(setList.isEmpty()) { 12 setList.insertFront(c); 13 }else { 14 ListNode currentNode=setList.front(); 15 while(currentNode.isValidNode()) { 16 if(((Comparable)currentNode.item()).compareTo(c)==0) { 17 break; 18 }else if(((Comparable)currentNode.item()).compareTo(c)>0) { 19 currentNode.insertBefore(c); 20 break; 21 }else if(!currentNode.next().isValidNode()){ 22 currentNode.insertAfter(c); 23 break; 24 } 25 currentNode=currentNode.next(); 26 } 27 } 28 }catch(InvalidNodeException e) { 29 System.out.println(e); 30 } 31 } 32 33 /** 34 * union() modifies this Set so that it contains all the elements it 35 * started with, plus all the elements of s. The Set s is NOT modified. 36 * Make sure that duplicate elements are not created. 37 * 38 * Performance: Must run in O(this.cardinality() + s.cardinality()) time. 39 * 40 * Your implementation should NOT copy elements of s or "this", though it 41 * will copy _references_ to the elements of s. Your implementation will 42 * create new _nodes_ for the elements of s that are added to "this", but 43 * you should reuse the nodes that are already part of "this". 44 * 45 * DO NOT MODIFY THE SET s. 46 * DO NOT ATTEMPT TO COPY ELEMENTS; just copy _references_ to them. 47 **/ 48 public void union(Set s) { 49 // Your solution here. 50 if(s != null && !s.setList.isEmpty()){ 51 ListNode curNode = setList.front(); 52 ListNode sNode = s.setList.front(); 53 Comparable curItem, sItem; 54 try{ 55 while(curNode.isValidNode() && sNode.isValidNode()){ 56 curItem = (Comparable)curNode.item(); 57 sItem = (Comparable)sNode.item(); 58 if(curItem.compareTo(sItem) == 0){ 59 60 sNode = sNode.next(); 61 }else if(curItem.compareTo(sItem) < 0){ 62 if(curNode.next().isValidNode()) { 63 curNode = curNode.next();} 64 else { 65 curNode.insertAfter(sItem); 66 curNode=curNode.next(); 67 sNode = sNode.next(); 68 } 69 }else{ 70 curNode.insertBefore(sItem); 71 sNode = sNode.next(); 72 73 } 74 } 75 }catch(InvalidNodeException e){ 76 System.err.println("union() failed"); 77 } 78 } 79 } 80 /** 81 * intersect() modifies this Set so that it contains the intersection of 82 * its own elements and the elements of s. The Set s is NOT modified. 83 * 84 * Performance: Must run in O(this.cardinality() + s.cardinality()) time. 85 * 86 * Do not construct any new ListNodes during the execution of intersect. 87 * Reuse the nodes of "this" that will be in the intersection. 88 * 89 * DO NOT MODIFY THE SET s. 90 * DO NOT CONSTRUCT ANY NEW NODES. 91 * DO NOT ATTEMPT TO COPY ELEMENTS. 92 **/ 93 public void intersect(Set s) { 94 // Your solution here. 95 ListNode curNode = setList.front(); 96 ListNode sNode = s.setList.front(); 97 Comparable curItem, sItem; 98 try{ 99 while(curNode.isValidNode()){ 100 if (!sNode.isValidNode()){ 101 ListNode node=curNode; 102 curNode=curNode.next(); 103 node.remove(); 104 105 }else { 106 curItem = (Comparable)curNode.item(); 107 sItem = (Comparable)sNode.item(); 108 if(curItem.compareTo(sItem) == 0){ 109 curNode = curNode.next(); 110 sNode = sNode.next(); 111 }else if(curItem.compareTo(sItem) < 0){ 112 ListNode node=curNode; 113 curNode=curNode.next(); 114 node.remove(); 115 116 }else if(curItem.compareTo(sItem) > 0){ 117 sNode = sNode.next(); 118 } 119 } 120 } 121 }catch(InvalidNodeException e){ 122 System.err.println("intersect() failed."); 123 } 124 125 }
结果：
