cn.cheny.toolbox.other.skiplist.SkipList Maven / Gradle / Ivy
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A personal java tool package project
package cn.cheny.toolbox.other.skiplist;
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import java.util.Random;
/**
* 数据结构：跳表
*
* @author cheney
*/
public class SkipList> {
/**
* 默认层数
*/
protected static final int DEFAULT_MAX_HIGH = 32;
/**
* 第0层头节点
*/
private Node head;
/**
* 第0层尾节点
*/
private Node tail;
private int size;
private int high;
private final int maxHigh;
protected static class Node> {
private final int high;
private T value;
private Node pre;
private Node[] next;
@SuppressWarnings("unchecked")
Node(T value, int high) {
this.value = value;
this.high = high;
this.next = new Node[high];
}
public T getValue() {
return value;
}
public void setValue(T value) {
this.value = value;
}
public Node getPre() {
return pre;
}
public void setPre(Node pre) {
this.pre = pre;
}
public Node[] getNext() {
return next;
}
public void setNext(Node[] next) {
this.next = next;
}
public void setNext(Node next, int high) {
this.next[high] = next;
}
public int getHigh() {
return high;
}
public void clear() {
this.value = null;
this.next = null;
this.pre = null;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Node node = (Node) o;
return new EqualsBuilder().append(high, node.high).append(value, node.value).isEquals();
}
@Override
public int hashCode() {
return new HashCodeBuilder(17, 37).append(high).append(value).toHashCode();
}
@Override
public String toString() {
return "Node{" +
"value=" + value +
'}';
}
}
public SkipList() {
this(DEFAULT_MAX_HIGH);
}
public SkipList(int maxHigh) {
if (maxHigh <= 1) {
throw new IllegalArgumentException("illegal arg max high,must gt 1");
}
this.maxHigh = maxHigh;
init();
}
private void init() {
this.size = this.high = 0;
// 初始化head
this.head = new Node<>(null, this.maxHigh);
}
/**
* 往跳表新增值
*
* @param value 新增值
*/
public void add(T value) {
if (value == null) {
throw new IllegalArgumentException("value can not be null");
}
int level = randomLevel();
Node n = new Node<>(value, level);
Node cur = this.head;
for (int i = level - 1; i >= 0; i--) {
Node next;
while ((next = cur.getNext()[i]) != null &&
next.value.compareTo(value) <= 0) {
cur = next;
}
if (cur.value != null && cur.value.compareTo(value) == 0
&& replaceWhileExists()) {
cur.value = value;
return;
}
// 新节点插入到update之后，originNext之前
Node originNext = cur.getNext()[i];
n.setNext(originNext, i);
cur.setNext(n, i);
}
// 更新pre,tail
n.setPre(cur);
Node next = n.getNext()[0];
if (next == null) {
this.tail = n;
} else {
next.setPre(n);
}
// 更新high,size
if (level > this.high) {
this.high = level;
}
size++;
}
/**
* 通过调表查询与入参值相等的数据
*
* @param target 查找的数据
* @return 是否存在
*/
public T get(T target) {
Node node = getNode(target);
return node == null ? null : node.getValue();
}
/**
* 通过调表查询与入参值相等的数据，不存在时返回其上一个数据
*
* @param target 查找的数据
* @return 是否存在
*/
public T getTargetOrPre(T target) {
Node node = getTargetOrPreNode(target);
return node == null ? null : node.getValue();
}
/**
* 通过调表查询是否存在数据
*
* @param target 查找的数据
* @return 是否存在
*/
public boolean contains(T target) {
return getNode(target) != null;
}
/**
* 删除所有与目标数据相同的节点
*
* @param target 删除的数据值
* @return 是否执行删除
*/
public boolean remove(T target) {
if (target == null) {
throw new IllegalArgumentException("value can not be null");
}
boolean flag = false;
int curLevel = high - 1;
Node cur = head;
while (curLevel >= 0) {
Node next;
while ((next = cur.getNext()[curLevel]) != null) {
int compare = next.value.compareTo(target);
if (compare < 0) {
cur = next;
} else if (compare == 0) {
// remove next
Node delNext = next.getNext()[curLevel];
if (delNext != null && delNext.pre == next) {
delNext.setPre(cur);
}
cur.setNext(delNext, curLevel);
flag = true;
} else {
break;
}
}
curLevel--;
}
return flag;
}
/**
* 查找与目标数据相同的节点，然后找出其偏移量为offset的数据
*
* @param target 删除的数据值
* @return 是否执行删除
*/
public T offset(T target, int offset) {
Node targetOrPreNode = getTargetOrPreNode(target);
if (targetOrPreNode == null) {
return null;
}
int curOffset = offset;
Node offsetNode = targetOrPreNode;
while (curOffset != 0 && offsetNode != null) {
if (curOffset > 0) {
offsetNode = offsetNode.getNext()[0];
curOffset--;
} else {
if (curOffset != -1) {
offsetNode = offsetNode.pre;
}
curOffset++;
}
}
return offsetNode == null ? null : offsetNode.value;
}
/**
* 返回跳表长度
*
* @return 跳表长度
*/
public int size() {
return size;
}
/**
* 通过跳表查询数据
*
* @param target 查找的数据
* @return 数据节点
*/
protected Node getNode(T target) {
Node targetOrPreNode = getTargetOrPreNode(target);
if (targetOrPreNode == null || targetOrPreNode.value.compareTo(target) != 0) {
return null;
}
return targetOrPreNode;
}
/**
* 通过跳表查询数据,不存在时返回其上一个节点
*
* @param target 查找的数据
* @return 数据节点
*/
protected Node getTargetOrPreNode(T target) {
if (target == null) {
return null;
}
int curLevel = high - 1;
Node cur = head;
while (curLevel >= 0) {
Node next;
while ((next = cur.getNext()[curLevel]) != null) {
int compare = next.value.compareTo(target);
if (compare < 0) {
cur = next;
} else if (compare == 0) {
return next;
} else {
break;
}
}
curLevel--;
}
return cur;
}
/**
* 存在时是否替换
*
* @return 默认返回false
*/
protected boolean replaceWhileExists() {
return false;
}
/**
* 抛硬币，每抛一次正面增加一层
* 最大MAX_HIGH层
*
* @return 层级
*/
private int randomLevel() {
Random random = new Random();
int level = 1;
int maxHigh = this.maxHigh;
for (int i = 1; i < maxHigh; i++) {
if ((random.nextInt(2) & 1) == 1) {
level++;
}
}
return level;
}
@Override
public String toString() {
StringBuilder print = new StringBuilder();
for (int i = high - 1; i >= 0; i--) {
if (i == 0) {
print.append("head--->");
} else {
print.append("\t\t");
}
Node cur = this.head;
int l = print.length();
while ((cur = cur.getNext()[i]) != null) {
print.append(cur.value).append("-----");
}
if (print.length() > l) {
print.setLength(print.length() - 5);
}
if (i == 0) {
print.append("--->tail");
} else {
print.append("\r\n");
}
}
return print.toString();
}
}
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