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99 lines (81 loc) · 2.42 KB
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package leetcode.hard.page5;
import java.util.Objects;
import java.util.Random;
public class Skiplist {
private static final int MAX_LEVEL = 16;
private Random r = new Random();
private Node head = new Node(MAX_LEVEL);
private int levelCount = 1;
public Skiplist() {
}
public boolean search(int target) {
Node p = head;
for (int i = levelCount - 1; i >= 0; --i) {
while (Objects.nonNull(p.next[i]) && p.next[i].data < target) {
p = p.next[i];
}
}
if (Objects.nonNull(p.next[0]) && p.next[0].data == target) {
return true;
} else {
return false;
}
}
public void add(int num) {
int level = Objects.isNull(head.next[0]) ? 1 : randomLevel();
if (level > levelCount) {
level = ++levelCount;
}
Node newNode = new Node(level);
newNode.data = num;
Node update[] = new Node[level];
for (int i = 0; i < level; ++i) {
update[i] = head;
}
Node p = head;
for (int i = level - 1; i >= 0; --i) {
while (Objects.nonNull(p.next[i]) && p.next[i].data < num) {
p = p.next[i];
}
update[i] = p;
}
for (int i = 0; i < level; ++i) {
newNode.next[i] = update[i].next[i];
update[i].next[i] = newNode;
}
}
public boolean erase(int num) {
Node[] update = new Node[levelCount];
Node p = head;
for (int i = levelCount - 1; i >= 0; --i) {
while (Objects.nonNull(p.next[i]) && p.next[i].data < num) {
p = p.next[i];
}
update[i] = p;
}
if (Objects.nonNull(p.next[0]) && p.next[0].data == num) {
for (int i = levelCount - 1; i >= 0; --i) {
if (Objects.nonNull(update[i].next[i]) && update[i].next[i].data == num) {
update[i].next[i] = update[i].next[i].next[i];
}
}
return true;
} else {
return false;
}
}
/**
* Need to optimize
* @return
*/
private int randomLevel() {
return (int) Math.floor(r.nextInt(MAX_LEVEL)) + 1;
}
class Node {
private int data = -1;
private Node[] next;
public Node(int level) {
next = new Node[level];
}
}
}