LeetCode 第1206题设计跳表

最新推荐文章于 2024-07-25 16:35:35 发布

、sakura

最新推荐文章于 2024-07-25 16:35:35 发布

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CC 4.0 BY-SA版权

文章标签： leetcode 算法

本文链接：https://blog.youkuaiyun.com/sakuraSD/article/details/124089152

本文介绍了如何使用Java实现LeetCode中的跳表数据结构，包括节点管理、插入、搜索和删除操作，通过工厂方法动态调整层数，以提升查询效率。虽然初始版本稍显缓慢，但优化后的解决方案将展示高效的数据结构设计技巧。

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LeetCode 第1206题设计跳表
思路来源：
LeetCode题解

class Solution {
    private static final float FACTORY = 0.25f;
    private static final int MAX_LEVEL = 32;
    private Node head = new Node(Integer.MIN_VALUE, MAX_LEVEL);
    private int level = 0;

    public Solution() {

    }
    public void add(int num) {
        int level = getLevel();
        if(level-1 > this.level){
            this.level = level-1;
        }
        Node node = new Node(num, level);
        for(int i = 0; i < level; i++) {
            Node temp = head;
            Node beforeNode = head;
            while (temp != null && temp.val < num){
                beforeNode = temp;
                temp = temp.next[i];
            }
            if(temp == null){
                beforeNode.next[i] = node;
            }else{
                if(temp.val >= num){
                    beforeNode.next[i] = node;
                    node.next[i] = temp;
                }
            }
        }
    }

    public boolean search(int target) {
        Node temp = head;
        Node beforeNode = head;
        for(int i = level; i >= 0; i--){
            while(temp != null && temp.val < target){
                beforeNode = temp;
                temp = temp.next[i];
            }
            if(temp == null){
                if(i == 0){
                    return false;
                }
                temp = beforeNode.next[i-1];
                continue;
            }else{
                if(temp.val == target){
                    return true;
                }
                if(temp.val > target){
                    if(i == 0){
                        return false;
                    }
                    temp = head;
                }
            }
        }
        return false;
    }

    public boolean erase(int num) {
        boolean flag = false;
        Node temp = head;
        Node beforeNode = head;
        for(int i = level; i >= 0; i--){
            while(temp != null && temp.val < num){
                beforeNode = temp;
                temp = temp.next[i];
            }
            if(temp == null){
                if(i == 0){
                    return false;
                }
                temp = beforeNode.next[i-1];
                continue;
            }
            if(temp.val >= num){
                if(temp.val == num){
                    beforeNode.next[i] = temp.next[i];
                    flag = true;
                }
                beforeNode = head;
                temp = head;
                continue;
            }
        }
        return flag;
    }

    private int getLevel() {
        int level = 1;
        while(Math.random() < FACTORY && level < MAX_LEVEL) {
            level++;
        }
        return level;
    }
}

class Node{
    int val;
    Node[] next;

    public Node(Integer val, int level) {
        this.val = val;
        this.next = new Node[level];
    }
}