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| public class MySkipList<K extends Comparable<? super K>,V>{
private MySkipListNode<K,V> head,tail;//头尾指针
private int nodeNum,levelNum;
private Random random;
private static final double PROBABILITY = 0.5;
private final K HEAD_KEY,TAIL_KEY;
public MySkipList(Class<K> kClass) {
random = new Random();
HEAD_KEY= (K) new NullComparable();
TAIL_KEY= (K) new NullComparable();
head = new MySkipListNode<>(HEAD_KEY,null);
tail = new MySkipListNode<>(TAIL_KEY,null);
horizontalLink(head,tail);
}
public int size(){
return nodeNum;
}
/**
* 在最底层找到要插入位置的元素
* @param key
* @return
*/
private MySkipListNode<K,V> findNode(K key){
MySkipListNode<K,V> node = head;
while (true){
while (node.right.key!=TAIL_KEY&&node.right.key.compareTo(key)<=0){
node = node.right;
}
if (node.down != null){
node = node.down;
}else {
break;
}
}
return node;
}
public MySkipListNode<K,V> get(K key){
MySkipListNode<K,V> node =findNode(key);
if (key.compareTo(node.key)==0){
return node;
}
return null;
}
public boolean add(K key, V value){
if (Objects.isNull(key)){
throw new AssertionError("THE KEY CANNOT BE EMPTY");
}
//如果key存在则直接赋值
MySkipListNode<K,V> node = findNode(key);
if (!(node.key instanceof NullComparable)&&key.compareTo(node.key)==0){
node.value=value;
return true;
}
MySkipListNode<K,V> newNode = new MySkipListNode<>(key,value);
backLink(node,newNode);
int currentLevel = 0;
while(random.nextDouble()<PROBABILITY){
if (currentLevel>=levelNum){
levelNum++;
MySkipListNode<K,V> newHeadNode = new MySkipListNode<K,V>(HEAD_KEY,null);
MySkipListNode<K,V> newTailNode = new MySkipListNode<>(TAIL_KEY,null);
horizontalLink(newHeadNode,newTailNode);
verticalLink(newHeadNode,head);
verticalLink(newTailNode,tail);
head = newHeadNode;
tail = newTailNode;
}
while (node.up == null){
node = node.left;
}
node = node.up;
MySkipListNode<K,V> newUpNode = new MySkipListNode<>(key,null);
backLink(node,newUpNode);
verticalLink(newUpNode,newNode);
newNode = newUpNode;
currentLevel++;
}
nodeNum++;
return true;
}
public List<MySkipListNode> traverseKey(){
List<MySkipListNode> listNodes = new ArrayList<>();
if (nodeNum == 0){
return null;
}
MySkipListNode<K,V> node = head;
StringBuilder builder =new StringBuilder();
while (node.down!=null){
node = node.down;
}
while (node.left!=null){
node = node.left;
}
while (node.right!=null){
listNodes.add(node);
node = node.right;
}
return listNodes;
}
/**
* 将back插入到front的后面。
* @param front
* @param back
*/
public void backLink(MySkipListNode front,MySkipListNode back){
back.left = front;
back.right=front.right;
front.right.left=back;
front.right=back;
}
/**
* 垂直链接
* @param upNode
* @param downNode
*/
public void verticalLink(MySkipListNode<K,V> upNode,MySkipListNode<K,V> downNode){
upNode.down = downNode;
downNode.up = upNode;
}
/**
* 水平链接
* @param leftNode
* @param rightNode
*/
public void horizontalLink(MySkipListNode<K,V> leftNode,MySkipListNode<K,V> rightNode){
leftNode.right = rightNode;
rightNode.left = leftNode;
}
private static class MySkipListNode<K,V>{
private K key;
private V value;
private MySkipListNode<K,V> up,down,left,right;//上下左右
public MySkipListNode(K key, V value) {
this.key = key;
this.value = value;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
return key==((MySkipListNode)o).key;
}
@Override
public int hashCode() {
return key.hashCode();
}
@Override
public String toString() {
return "MySkipListNode{" +
"key=" + key +
", value=" + value +
'}';
}
}
private static class NullComparable implements Comparable{
@Override
public int compareTo(Object o) {
System.out.println(o);
return 0;
}
}
public static void main(String[] args) {
MySkipList<String,String> mySkipList = new MySkipList<>(String.class);
Random random = new Random();
for (int i=0;i<20;i++){
int num = random.nextInt(100);
System.out.println("num = "+num);
mySkipList.add(String.valueOf(num),"num="+num);
}
System.out.println(mySkipList.traverseKey());
}
}
|
