1206. 设计跳表

不使用任何库函数，设计一个 跳表 。

class Skiplist {int level=0;Node head=null;public Skiplist() {}public boolean search(int target) {Node cur=head;while(cur!=null){while(cur.right!=null&&cur.right.val<target){cur=cur.right;}if(cur.right!=null&&cur.right.val==target){return true;}cur=cur.down;}return false;}public void add(int num) {int rLevel=1;while(rLevel<=level&&(Math.random()%2)==1){rLevel++; // 2}if(rLevel>level){level=rLevel;head=new Node(num,null,head);}Node cur=head,last=null;for(int l=level;l>0;l--){while(cur.right!=null&&cur.right.val<num){cur=cur.right;}if(l<=rLevel){cur.right=new Node(num,cur.right,null);if(last!=null){last.down=cur.right;}last=cur.right;}cur=cur.down;}}// 擦除public boolean erase(int num) {Node cur=head;boolean seen=false;for(int l=level;l>0;l--){while(cur.right!=null&&cur.right.val<num){cur=cur.right;}if(cur.right!=null&&cur.right.val==num){seen=true;// Node tmp=cur.right;cur.right=cur.right.right;}cur=cur.down;}return seen;}
}/*** Your Skiplist object will be instantiated and called as such:* Skiplist obj = new Skiplist();* boolean param_1 = obj.search(target);* obj.add(num);* boolean param_3 = obj.erase(num);*/public class Node {public int val;public Node right,down;Node() {}public Node(int val) {this.val = val;}Node(int val, Node right,Node down) {this.val = val;this.right = right;this.down = down;}/*public void add(int value) {Node p = this;while (p.right != null) {p = p.right;}Node newNode = new Node(value);p.right = newNode;}public void add(Node node) {Node p = this;while (p.right != null) {p = p.right;}p.right = node;}*/
}