Vampirelzl的博客

ConcurrentHashMap 源码解析

Vampirelzl — Sat, 27 Aug 2022 18:39:21 +0800

JDK 1.8 中的 ConcurrentHashMap 源码解析

InnoDB的B+索引

Vampirelzl — Thu, 21 Jul 2022 23:24:53 +0800

本文主要讲述 B+ 树在 InnoDB 索引下的实现和产生的背景，不涉及 B+ 树节点的更新算法。

MySQL的数据页结构和记录的管理

Vampirelzl — Sun, 17 Jul 2022 15:27:43 +0800

MySQL 的页有多种类型，本文主要讲述数据页的结构和记录管理，数据页也就是表中一行一行的数据组成的页。

一条SQL语句的执行过程

Vampirelzl — Thu, 14 Jul 2022 16:03:49 +0800

本文站在后端开发的角度，讲述一条SQL从客户端发送到MySQL服务器进行处理，并将结果返回给客户端的过程。这个过程中涉及的操作会在后面的文章中做详细的分析。

Stream将List转成Map的坑

Vampirelzl — Sun, 02 Aug 2020 16:27:06 +0800

1. 背景常规 list 转 map 的方法： Map map = new HashMap<>(); for (User user : list) { map.put(user.getName(), user.getAddress()); } 这种方式没什么问题，就是代码不够简洁美观，而且逼格不够高。可以通过 Java8 中的 Stream 流来轻松实现这个功能。 Map map = list.s

Java 注解概论

Vampirelzl — Sun, 05 Jul 2020 17:34:37 +0800

Java 注解概论注解可以简化主流程代码，具体分为以下3个方面： 1.生成文档，在注释中随处可见，例如 @param，@return 等； 2.代替配置文件，Spring 框架经常使用注解来代替XML配置文件，精简代码结构； 3.编译时进行格式检查，例如 @Override； 1. 定义注解所有注解都继承了 Annotation 接口，但不是采用 implement 关键字实现，而是用 @interface 声明接口来实现继承的逻辑，表示这是一个注解。例如，常见的 @Override 注解。 @Targ

Java 函数式编程概论

Vampirelzl — Fri, 17 Apr 2020 23:38:28 +0800

1. 函数的基本概念函数就是将输入转换一种形式进行输出。以数学中的函数为例，假设有一个函数 f(x)=3x+1f(x) = 3x + 1f(x)=3x+1，当输入 x=1x = 1x=1 时，输出 f(x)=4f(x) = 4f(x)=4。Java 中函数的概念类似，以 Comparator 类为例，下面代码是一个函数式接口。其中方法 applyAsInt 表示一种转换关系，相当于数学函数中的 ...

基于Anaconda的graphviz使用问题

Vampirelzl — Tue, 23 Jan 2018 12:28:41 +0800

想要用graphviz可视化sklearn生成的决策树，运行网上的例子提示无法找到graphviz.exe文件。在sklearn的官网中找到了解决办法。在cmd界面输入conda install python-graphviz来安装graphviz。举一个例子： from sklearn.datasets import load_iris from sklearn import tr

226. Invert Binary Tree Difficult: Easy

Vampirelzl — Fri, 03 Nov 2017 22:48:09 +0800

Invert a binary tree. 4 / \ 2 7 / \ / \ 1 3 6 9to 4 / \ 7 2 / \ / \ 9 6 3 1算法分析：可以用层序遍历的方法交换左右子树，也可以直接递归。C语言版struct TreeNode* invertTree(struct TreeNode* roo

Maximum Depth of Binary Tree

Vampirelzl — Sat, 28 Oct 2017 22:10:01 +0800

Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.算法解析：既可以用深度优先搜索，也可以用广度优先搜索，前者可以节省代码，后者可以提高速

695. Max Area of Island Difficulty: Easy

Vampirelzl — Sat, 28 Oct 2017 21:28:22 +0800

Given a non-empty 2D array grid of 0’s and 1’s, an island is a group of 1’s (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surroun

526. Beautiful Arrangement Difficulty: Medium

Vampirelzl — Sat, 28 Oct 2017 21:13:22 +0800

Suppose you have N integers from 1 to N. We define a beautiful arrangement as an array that is constructed by these N numbers successfully if one of the following is true for the ith position (1 <= i <

136. Single Number Difficulty: Medium

Vampirelzl — Sat, 14 Oct 2017 09:49:01 +0800

Given an array of integers, every element appears twice except for one. Find that single one.Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra me

515. Find Largest Value in Each Tree Row Difficulty: Medium

Vampirelzl — Fri, 13 Oct 2017 15:42:28 +0800

You need to find the largest value in each row of a binary tree.Example:Input: 1 / \ 3 2 / \ \ 5 3 9 Output: [1, 3, 9]算法分析：考查BFS，或者说是树的层序遍历，但要注意区分每一层。我

647. Palindromic Substrings Difficulty: Medium

Vampirelzl — Thu, 12 Oct 2017 14:04:10 +0800

Given a string, your task is to count how many palindromic substrings in this string.The substrings with different start indexes or end indexes are counted as different substrings even they consist of

540. Single Element in a Sorted Array Difficulty：Medium

Vampirelzl — Wed, 11 Oct 2017 20:33:46 +0800

Given a sorted array consisting of only integers where every element appears twice except for one element which appears once. Find this single element that appears only once.Example 1:Input: [1,1,2,3,3

406. Queue Reconstruction by Height Difficulty : Medium

Vampirelzl — Tue, 10 Oct 2017 21:18:14 +0800

Suppose you have a random list of people standing in a queue. Each person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this p

442. Find All Duplicates in an Array Difficulty : Medium

Vampirelzl — Tue, 10 Oct 2017 19:17:07 +0800

Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.Find all the elements that appear twice in this array.Could you do it without extra space

513. Find Bottom Left Tree Value Difficulty : mediate

Vampirelzl — Wed, 04 Oct 2017 23:06:39 +0800

Given a binary tree, find the leftmost value in the last row of the tree.Example 1:Input: 2 / \ 1 3Output: 1Example 2: Input: 1 / \ 2 3 / / \ 4 5 6

463. Island Perimeter Difficulty : Easy

Vampirelzl — Tue, 03 Oct 2017 11:46:40 +0800

You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/vertically (not diagonally). The grid is completely s