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原创 Paxos 算法分析

Paxos 的核心思想：“与其预测未来，不如限制未来”。背景：Paxos算法是莱斯利·兰伯特（英语：Leslie Lamport，LaTeX中的“La”）于1990年提出的一种基于消息传递且具有高度容错特性的共识（consensus）算法。分布式系统中的节点通信存在两种模型：共享内存（Shared memory）和消息传递（Messages passing）。基于消息传递通信模型的分布式系统，不可避免的会发生以下错误：进程可能会慢、被杀死或者重启，消息可能会延迟、丢失、重复，在基础 .

2020-07-22 20:03:53 326

原创并查集算法（Union find）第二式：加权quick-union

参考：《算法》第四版，p144- p146以leetcode, 200th : Number of Islands() 为例 (https://leetcode.com/problems/number-of-islands/)对于加权quick-union算法，N个触点，在最坏情况下，find()、union()、isConnected()的成本增长数量级为lgNpackage...

2020-03-31 18:49:34 197

原创并查集算法（Union find）第一式：quick-union

参考：《算法》第四版，p136 - p144以leetcode, 200th : Number of Islands() 为例 (https://leetcode.com/problems/number-of-islands/)package com.odyssey.app.algorithm.base;/** * 并查集算法 - 以lc200，number of island...

2020-03-29 16:59:21 168

原创 JVM - 老年代垃圾收集器CMS产生的问题分析

Concurrent Mark Sweep 垃圾收集器，GC 过程中不可避免的问题：1、 promotion failed2、concurrent mode failureGC 日志举例：106.641: [GC 106.641: [ParNew (promotion failed): 14784K->14784K(14784K), 0.0370328 secs]106...

2019-10-30 20:14:38 600

原创 Snowflake 算法分析与Java实现（参考 Twitter 官方 Scala 原版实现）

参考：Twitter 官方 Scala 原版实现https://github.com/twitter-archive/snowflakepackage com.app.main.snowflake;/** * Created with IDEA * author:Dingsheng Huang * Date:2019/8/4 * Time:下午4:28 * *...

2019-08-04 17:48:31 210

转载 SDE的核心能力-抽象思维

新技术变化太快,稍不留意就陷入了追逐乱七八糟技术的泥潭中,还洋洋得意的认为自己在持续学习,然而实际上并没有沉淀出有意义的东西,切忌多思考价值.程序员要掌握的知识，要具备的能力实在太多，多得头发都不够掉。大体有两大方向。一是对工具的熟练掌握，如操作系统、网络、IO、编程语言等；另一个是用代码为现实问题生成解决方案的能力，这其中最重要的是抽象能力。前一个方向是很容易意识到的，很多现象可以说...

2019-04-28 21:10:08 399

原创 LeetCode--medium--interleaving_string_97

summary:divide and conquer | memorizationpackage myapp.kit.leetcode.top200;import java.util.HashMap;import java.util.Map;/** * * 97 * hard * https://leetcode.com/problems/interleaving-string/ * * Given s1, s2, s3, find whether s3 is formed

2020-07-22 19:45:11 258

原创 LeetCode--medium--valid_number_65

summary:DFApackage myapp.kit.leetcode.top200;import java.util.HashMap;import java.util.HashSet;import java.util.Map;import java.util.Set;/** * * 65 * hard * https://leetcode.com/problems/valid-number/ * * Validate if a given string can be

2020-07-22 19:43:32 242

原创 LeetCode--medium--search_in_rotated_array_ii_81

summary:binary searchpackage myapp.kit.leetcode.top200;/** * 81 * medium * https://leetcode.com/problems/search-in-rotated-sorted-array-ii/ * * Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. * *

2020-07-22 19:40:52 130

原创 LeetCode--medium--scramble_string_87

summary:divide and conquer | memorizationpackage myapp.kit.leetcode.top200;import java.util.HashMap;import java.util.Map;/** * 87 * hard *https://leetcode.com/problems/scramble-string/ * * Given a string s1, we may represent it as a binary

2020-07-22 19:39:53 106

原创 LeetCode--medium--rotate_list_61

summary:two pointerspackage myapp.kit.leetcode.top200;import myapp.kit.leetcode.base.ListNode;/** * * 61 * medium * https://leetcode.com/problems/rotate-list/ * * Given a linked list, rotate the list to the right by k places, where k is non-

2020-07-22 19:37:47 100

原创 LeetCode--medium--remove_duplicates_from_sorted_list_83

summary:linked listpackage myapp.kit.leetcode.top200;import myapp.kit.leetcode.base.ListNode;/** * 83 * easy *https://leetcode.com/problems/remove-duplicates-from-sorted-list/ * * Given a sorted linked list, delete all duplicates such that ea

2020-07-20 11:12:17 102

原创 LeetCode--medium--remove_duplicates_from_sorted_list_82

summary:linked listpackage myapp.kit.leetcode.top200;import myapp.kit.leetcode.base.ListNode;/** * 82 * medium * https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/ * * Given a sorted linked list, delete all nodes that have d

2020-07-20 11:11:20 88

原创 LeetCode--medium--remove_duplicates_from_sorted_array_ii_80

summary:arraypackage myapp.kit.leetcode.top200;/** * * * 80 * medium * https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/ * * Given a sorted array nums, remove the duplicates in-place such that duplicates appeared at most t

2020-07-20 11:10:31 110

原创 LeetCode--medium--permutation_sequence_60

/** * summary: * approach 1 : dfs backtrack but TLE ! * * approach 2 : math * candidate: [1,2,3,4,...n] kth * 1. calculate block size : (n - 1)! * 2. renew candidate and k * new k = k % (n - 1)! * .

2020-07-20 11:08:30 103

原创 LeetCode--medium--partition_list_86

summary:divide and conquer | two pointerspackage myapp.kit.leetcode.top200;import myapp.kit.leetcode.base.ListNode;/** * * 86 * medium * https://leetcode.com/problems/partition-list/ * * * Given a linked list and a value x, partition it suc

2020-07-20 11:05:57 77

原创 LeetCode--medium--n_queens_ii_52

summary:backtrackpackage myapp.kit.leetcode.top200;import java.util.ArrayList;import java.util.List;/** * * 52 * hard * https://leetcode.com/problems/n-queens-ii/ * * The n-queens puzzle is the problem of placing n queens on an n×n chessboa

2020-07-20 11:04:50 116

原创 LeetCode--medium--n_queens_51

summary:backtrackpackage myapp.kit.leetcode.top200;import java.util.ArrayList;import java.util.List;/** * * 51 * hard *https://leetcode.com/problems/n-queens/ * The n-queens puzzle is the problem of placing n queens on an n×n chessboard such

2020-07-20 11:03:50 99

原创 LeetCode--medium--multiply_strings_43

summary:handle carrypackage myapp.kit.leetcode.top200;/** * 43 * medium * https://leetcode.com/problems/multiply-strings/ * * Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, * also rep

2020-07-20 11:02:55 138

原创 LeetCode--medium--combinations_77

summary:combinations | backtrackpackage myapp.kit.leetcode.top200;import java.util.ArrayList;import java.util.List;/** * * 77 * medium * https://leetcode.com/problems/combinations/ * * Given two integers n and k, return all possible combina

2020-07-20 11:01:42 103

原创 LeetCode--medium--add_binary_67

summary:handle carrypackage myapp.kit.leetcode.top200;/** * * 67 * medium * https://leetcode.com/problems/add-binary/ * * Given two binary strings, return their sum (also a binary string). * * The input strings are both non-empty and contain

2020-07-20 11:00:31 83

原创 Java map 优雅的元素遍历方式

Java 8 , Lambda + foreach 语法糖, 写起来非常的 cleanpublic static void main(String[] args) { // map init Map<String, String> map = new HashMap<>(); map.put("k", "v"); /*=====处理函数只有单条语句=====*/ map.forEach((k...

2020-07-03 17:32:17 756

原创 LeetCode--12--medium--IntegerToRoman

summary:classified discussionpackage myapp.kit.leetcode.top200;/** * 12 * medium * https://leetcode.com/problems/integer-to-roman/ * * Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. * * Symbol Value

2020-06-29 21:40:56 116

原创 mysql 按天、周、月分组查询【sql模板】

1. 按天统计： select DATE_FORMAT(create_time, '%Y%m%d') days, count(id) from xxx_table group days;2. 按周统计： select DATE_FORMAT(create_time,'%Y%u') weeks,count(id) fromxxx_table group by weeks; 3. 按月统计 select DATE_FORMAT(create_time,...

2020-06-29 21:26:55 958

原创 mysql 日期与时间戳转换【sql 模板】

1.日期 ---> 时间戳（秒）selectUNIX_TIMESTAMP('2020-07-01 12:00:00')输出：15935760002. 时间戳（秒）---> 日期select FROM_UNIXTIME(1593576000)输出：2020-07-01 12:00:00

2020-06-28 11:04:55 319

原创 mysql查询字段长度 | length()、char_length()函数说明

1. MySQL5.0.3版本之后varchar类型的变化　　1）、MySQL 5.0.3 之前：0-255字节，如：varchar(20)中的20表示字节数，如果存放utf-8编码的话只能放6个汉字。varchar(n)，这里的n表示字节数。　　　　MySQL 5.0.3 之后：0-65535字节，varchar(20)表示字符数，不管什么编码，既汉字也能放20个。但最多占65532字节（两个字节存放长度，小于255字节用1个字节存放长度），varchar(n)这里的n表示字符数，比如varchar

2020-06-22 21:58:47 12219

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