/*
跳跃表的实现 75+68
*/
static class Skiplist {
class Node {
int val;
Node right,down;
public Node(Node r, Node d, int val) {
right = r;
down = d;
this.val = val;
}
}
public Skiplist() {
this.head=new Node(null, null, 0);
this.rand = new Random();
this.maxLevel=64;
nodeList=new Node[maxLevel];
}
/*
头结点默认为0值的结点,头结点之间通过down连接
每一行都有一个头结点,类似于前驱哨兵结点
*/
Node head ;
Random rand;
int maxLevel; // 链表的最大层数
Node[] nodeList;// 添加结点时,路径的记录
public boolean search(int target) {
// 先往右再往下,缩小区间
for (Node p=head;p!=null;p=p.down) {
while (p.right!=null&&p.right.val<target){
p=p.right;
}
if (p.right!=null&&p.right.val==target){
return true;
}
}
return false;
}
public void add(int num) {
int lv = -1;
// 遍历每一层的哨兵头结点
for (Node p = head; p != null; p = p.down) {
while (p.right != null && p.right.val < num) {
p = p.right;
}
// 记录每次向下进行的路径结点
nodeList[++lv] = p;
}
boolean insertUp = true;
Node downNode = null;
// lv-- 每次向上一层
while (insertUp && lv >= 0) {
Node insert = nodeList[lv--]; // 新添加结点前一个结点
insert.right = new Node(insert.right, downNode, num);
downNode = insert.right; // downNode就是新添加的结点
insertUp = (rand.nextInt() & 1) == 0; // 按一定的几率是否继续向上添加一行
}
// 是否在当前已有行的最上面再增加一行,最上面一行哨兵结点就是头结点
// 最后往上增加链表层数
if (insertUp) {
head = new Node(new Node(null, downNode, num), head, 0);
}
}
/*
在跳表中删除一个值,如果 num 不存在,直接返回false. 如果存在多个 num ,删除其中任意一个即可
*/
public boolean erase(int num) {
boolean exists = false;
// 遍历每一层找到相同值的结点,只删除一个
for (Node p = head; p != null; p = p.down) {
while (p.right != null && p.right.val < num) {
p = p.right;
}
if (p.right != null && p.right.val == num) {
exists = true;
p.right = p.right.right;
}
}
return exists;
}
}
public static void main(String[] args) {
Skiplist skiplist=new Skiplist();
System.out.println(skiplist.search(2));
skiplist.add(50);
skiplist.add(50);
skiplist.add(60);
skiplist.erase(50);
System.out.println(skiplist.search(50));
}
别人的代码加上注释,微改动,图自己手画