@@ -56,22 +56,264 @@ skiplist.search(1); // 返回 false,1 已被擦除
5656
5757<!-- 这里可写通用的实现逻辑 -->
5858
59+ 因为节点 ` level ` 随机,所以需要多个 ` next ` 指针,其余操作类似单链表
60+ 5961<!-- tabs:start -->
6062
6163### ** Python3**
6264
6365<!-- 这里可写当前语言的特殊实现逻辑 -->
6466
6567``` python
66- 68+ class Node :
69+ def __init__ (self val : int , level : int ):
70+ self .val = val
71+ self .next = [None for _ in range (level)]
72+ 73+ 74+ class Skiplist :
75+ max_level = 16
76+ p = 0.5
77+ 78+ def __init__ (self
79+ self .head = Node(- 1 , self .max_level)
80+ self .level = 1
81+ 82+ def search (self target : int ) -> bool :
83+ p = self .head
84+ for i in range (self .level - 1 , - 1 , - 1 ):
85+ p = self .find_closest(p, i, target)
86+ if p.next[i] != None and p.next[i].val == target:
87+ return True
88+ return False
89+ 90+ def add (self num : int ) -> None :
91+ level = self .random_level()
92+ self .level = max (self .level, level)
93+ node = Node(num, level)
94+ p = self .head
95+ for i in range (self .level - 1 , - 1 , - 1 ):
96+ p = self .find_closest(p, i, num)
97+ if i < level:
98+ node.next[i] = p.next[i]
99+ p.next[i] = node
100+ 101+ def erase (self num : int ) -> bool :
102+ ok = False
103+ p = self .head
104+ for i in range (self .level - 1 , - 1 , - 1 ):
105+ p = self .find_closest(p, i, num)
106+ if p.next[i] != None and p.next[i].val == num:
107+ p.next[i] = p.next[i].next[i]
108+ ok = True
109+ while self .level > 1 and self .head.next[self .level - 1 ] == None :
110+ self .level -= 1
111+ return ok
112+ 113+ def find_closest (self p : Node, level : int , target : int ) -> Node:
114+ while p.next[level] != None and p.next[level].val < target:
115+ p = p.next[level]
116+ return p
117+ 118+ def random_level (self int :
119+ level = 1
120+ while level < self .max_level and random.random() < self .p:
121+ level += 1
122+ return level
123+ 124+ 125+ # Your Skiplist object will be instantiated and called as such:
126+ # obj = Skiplist()
127+ # param_1 = obj.search(target)
128+ # obj.add(num)
129+ # param_3 = obj.erase(num)
67130```
68131
69132### ** Java**
70133
71134<!-- 这里可写当前语言的特殊实现逻辑 -->
72135
73136``` java
137+ class Skiplist {
138+ 139+ private static final int DEFAULT_MAX_LEVEL = 16 ;
140+ private static final double DEFAULT_P_FACTOR = 0.5 ;
141+ 142+ private final Node head;
143+ private int currentLevel;
144+ 145+ public Skiplist () {
146+ this . head = new Node (0 , DEFAULT_MAX_LEVEL );
147+ this . currentLevel = 1 ;
148+ }
149+ 150+ public boolean search (int target ) {
151+ Node node = head;
152+ for (int i = currentLevel - 1 ; i >= 0 ; i-- ) {
153+ node = findClosest(node, i, target);
154+ if (node. next[i] != null && node. next[i]. value == target) {
155+ return true ;
156+ }
157+ }
158+ return false ;
159+ }
160+ 161+ public void add (int num ) {
162+ int level = randomLevel();
163+ currentLevel = Math . max(currentLevel, level);
164+ Node newNode = new Node (num, level);
165+ Node updateNode = head;
166+ for (int i = currentLevel - 1 ; i >= 0 ; i-- ) {
167+ updateNode = findClosest(updateNode, i, num);
168+ if (i < level) {
169+ newNode. next[i] = updateNode. next[i];
170+ updateNode. next[i] = newNode;
171+ }
172+ }
173+ }
174+ 175+ public boolean erase (int num ) {
176+ boolean exist = false ;
177+ Node node = head;
178+ for (int i = currentLevel - 1 ; i >= 0 ; i-- ) {
179+ node = findClosest(node, i, num);
180+ if (node. next[i] != null && node. next[i]. value == num) {
181+ node. next[i] = node. next[i]. next[i];
182+ exist = true ;
183+ }
184+ }
185+ while (currentLevel > 1 && head. next[currentLevel - 1 ] == null ) {
186+ currentLevel-- ;
187+ }
188+ return exist;
189+ }
190+ 191+ private Node findClosest (Node node , int level , int value ) {
192+ while (node. next[level] != null && node. next[level]. value < value) {
193+ node = node. next[level];
194+ }
195+ return node;
196+ }
197+ 198+ private int randomLevel () {
199+ int level = 1 ;
200+ while (level < DEFAULT_MAX_LEVEL && Math . random() < DEFAULT_P_FACTOR ) {
201+ level++ ;
202+ }
203+ return level;
204+ }
205+ 206+ static class Node {
207+ int value;
208+ Node [] next;
209+ 210+ Node (int value , int level ) {
211+ this . value = value;
212+ this . next = new Node [level];
213+ }
214+ }
215+ }
216+ ```
74217
218+ ### ** Go**
219+ 220+ ``` go
221+ func init () { rand.Seed (time.Now ().UnixNano ()) }
222+ 223+ const (
224+ maxLevel = 16
225+ p = 0.5
226+ )
227+ 228+ type node struct {
229+ val int
230+ next []*node
231+ }
232+ 233+ func newNode (val , level int ) *node {
234+ return &node{
235+ val: val,
236+ next: make ([]*node, level),
237+ }
238+ }
239+ 240+ type Skiplist struct {
241+ head *node
242+ level int
243+ }
244+ 245+ func Constructor () Skiplist {
246+ return Skiplist{
247+ head: newNode (-1 , maxLevel),
248+ level: 1 ,
249+ }
250+ }
251+ 252+ func (this *Skiplist ) Search (target int ) bool {
253+ p := this.head
254+ for i := this.level - 1 ; i >= 0 ; i-- {
255+ p = findClosest (p, i, target)
256+ if p.next [i] != nil && p.next [i].val == target {
257+ return true
258+ }
259+ }
260+ return false
261+ }
262+ 263+ func (this *Skiplist ) Add (num int ) {
264+ level := randomLevel ()
265+ if level > this.level {
266+ this.level = level
267+ }
268+ node := newNode (num, level)
269+ p := this.head
270+ for i := this.level - 1 ; i >= 0 ; i-- {
271+ p = findClosest (p, i, num)
272+ if i < level {
273+ node.next [i] = p.next [i]
274+ p.next [i] = node
275+ }
276+ }
277+ }
278+ 279+ func (this *Skiplist ) Erase (num int ) bool {
280+ ok := false
281+ p := this.head
282+ for i := this.level - 1 ; i >= 0 ; i-- {
283+ p = findClosest (p, i, num)
284+ if p.next [i] != nil && p.next [i].val == num {
285+ p.next [i] = p.next [i].next [i]
286+ ok = true
287+ }
288+ }
289+ for this.level > 1 && this.head .next [this.level -1 ] == nil {
290+ this.level --
291+ }
292+ return ok
293+ }
294+ 295+ func findClosest (p *node , level , target int ) *node {
296+ for p.next [level] != nil && p.next [level].val < target {
297+ p = p.next [level]
298+ }
299+ return p
300+ }
301+ 302+ func randomLevel () int {
303+ level := 1
304+ for level < maxLevel && rand.Float64 () < p {
305+ level++
306+ }
307+ return level
308+ }
309+ 310+ /* *
311+ * Your Skiplist object will be instantiated and called as such:
312+ * obj := Constructor();
313+ * param_1 := obj.Search(target);
314+ * obj.Add(num);
315+ * param_3 := obj.Erase(num);
316+ */
75317```
76318
77319### ** ...**
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