# Prove Logs on Blockchain with Go and ProvenDB

It’s been a long time since my last blog post. Here is my recent one on Medium: ProvenLogs is a simple yet performant logging service built with Go and ProvenDB that can continuously prove your system logs on Blockchain Continue reading… Continue reading...

I just wrote my first Atom extension called file-header. It allows you to customize, add, update and cooperate your authoring information in header comment like this: Continue reading...

According to Apple’s notes, the NSMutableDictionary is not safe if it is accessed from multiple threads simultaneously. To tackle this problem, one may choose to use a lock or a serial queue to synchronise access to a NSMutableDictionary. However, these approaches are pretty inefficient, especially in situations where reads happen much more often then writes. If Continue reading...

# Pure SQL Approach to Globally Search and Replace Strings in MySQL Database

Say, in MySQL, if you would like to find the string 'http://www.guiguan.net' in a database and replace all of its occurrences (from all columns/fields of all tables in the database) with another string 'https://www.guiguan.net', because that you just moved to a more secure world, then you can achieve this purely using native SQL statements in MySQL. First, launch your favourite MySQL Continue reading...

# LeetCode in Swift: Longest Palindromic Substring

Problem Statement Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring. Original LeetCode problem page My Solution in Swift Continue reading...

# LeetCode in Swift: Largest Rectangle in Histogram

Problem Statement Given n non-negative integers representing the histogram’s bar height where the width of each bar is 1, find the area of largest rectangle in the histogram. Above is a histogram where width of each bar is 1, given height = [2,1,5,6,2,3]. The largest rectangle is shown in the shaded area, which has area Continue reading...

# LeetCode in Swift: Word Search

Problem Statement Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where “adjacent” cells are those horizontally or vertically neighboring. The same letter cell may not be used more than once. For example, Given board =

# LeetCode in Swift: Reverse Words in a String

Problem Statement Given an input string, reverse the string word by word. For example: Given s = “ the sky is blue”, return “ blue is sky the”. Clarification: What constitutes a word? A sequence of non-space characters constitutes a word. Could the input string contain leading or trailing spaces? Yes. However, your reversed string should not contain leading or trailing spaces. How Continue reading...

# LeetCode in Swift: Binary Tree Level Order Traversal II

Problem Statement Given a binary tree, return the bottom-up level order traversal of its nodes’ values. (ie, from left to right, level by level from leaf to root). For example: Given binary tree {3,9,20,#,#,15,7},

return its bottom-up level order traversal as:

Original LeetCode problem page My Solution in Swift Continue reading...

# LeetCode in Swift: Binary Tree Level Order Traversal

Problem Statement Given a binary tree, return the level order traversal of its nodes’ values. (ie, from left to right, level by level). For example: Given binary tree {3,9,20,#,#,15,7},

return its level order traversal as:

Original LeetCode problem page My Solution in Swift Continue reading...