2013.12.28

* 条件语句中的判断部分，要把判断对象是否为null的表达式 写在 && 的最前面，这样保证 && 后的语句不会访问空引用；

* 突然发现学java好像在游戏里练级…你的代码行数就是经验值~求双倍，三倍，四倍经验！

* 实现了基于链地址法进行冲突处理的哈希表@java/DataStructure/unit11

class Data{
	private int key;
	private double data;

	public Data(int key, double data){
		this.key=key;
		this.data=data;
	}
	
	public Data(){
		key=0;
		data=0;
	}

	public int getKey(){
		return key;
	}

	public void setKey(int newKey){
		key=newKey;
	}

	public double getData(){
		return data;
	}

	public void display(){
		System.out.print("["+key+", "+data+"] ");
	}
}

class Link{
	private Data data;
	public Link next;

	public Link(Data data){
		this.data=data;
		next=null;
	}

	public Link(){
		data=null;
		next=null;
	}

	public Data getData(){
		return data;
	}

	public void display(){
		data.display();
	}
}

class LinkList{
	private Link head;

	public LinkList(){
		head=null;
	}

	public Link getHead(){
		return head;
	}

	public void insert(Link newLink){
		if(head==null) head=newLink;
		else{
			Link current=head;
			Link prev=head;
			while(current!=null && current.getData().getKey()<newLink.getData().getKey()){
				prev=current;
				current=current.next;
			}
			if(current==head){
				newLink.next=head;
				head=newLink;
			}
			else{
				prev.next=newLink;
				newLink.next=current;
			}
		}
	}

	public Link delete(int key){
		if(head==null){
			System.out.println("Can not Delete: Empty LinkList!");
			return null;
		}
		else{
			Link current=head;
			Link prev=current;
			while(current!=null && current.getData().getKey()!=key){
				prev=current;
				current=current.next;
			}
			if(current==null){
				System.out.println("Can not Delete: Not Found!");
				return null;
			}
			else if(current==head){
				Link temp=head;
				head=head.next;
				return temp;
			}
			else{
				prev.next=current.next;
				return current;
			}
		}

	}

	public Link find(int key){
		if(head==null){
			System.out.println("Can not Find: Empty LinkList!");
			return null;
		}
		else{
			Link current=head;
			while(current!=null && current.getData().getKey()!=key){
				current=current.next;
			}
			if(current==null){
				System.out.println("Can not Find: Not Exist!");
				return null;
			}
			else return current;
		}
	}

	public void display(){
		if(head==null){
			System.out.println("Empty List!");
			return;
		}
		Link current=head;
		int counter=0;
		while(current!=null){
			current.display();
			current=current.next;
			if(++counter==5){
				System.out.println();
				counter=0;
			}
		}
		System.out.println();
	}
}

class HashTable{
	private LinkList [] lArr;
	private int size;
	private int current;

	public HashTable(int max){
		lArr=new LinkList[max];
		size=max;
		current=0;
	}

	public void insert(Link newLink){
		int key=newLink.getData().getKey()%size;
		if(current==size){
			System.out.println("Can no Insert: The HashTable is Full!");
		}
		if(lArr[key]==null){
			lArr[key]=new LinkList();
			current++;
		}
		lArr[key].insert(newLink);
	}

	public Link delete(int key){
		int obj=key%size;
		if(lArr[obj]==null){
			System.out.println("Can not Delete: Not Exist!");
			return null;
		}
		else return lArr[obj].delete(key);
	}

	public Link find(int key){
		int obj=key%size;
		if(lArr[obj]==null){
			System.out.println("Can not Find: Not Exist!");
			return null;
		}
		else return lArr[obj].find(key);
	}

	public void display(){
		for(int i=0; i<size; i++){
			if(lArr[i]==null || lArr[i].getHead()==null){
				System.out.println("The "+i+" LinkList is Empty!");
				continue;
			}
			System.out.println("The "+i+" LinkList: ");
			lArr[i].display();
		}
	}
}