IntelliJ

写 Java 用 IntelliJ 可以让工程师 enjoy coding 而不是 typing.

我研究一番，发现学习 IntelliJ 直接 follow 内建的Learn IDE Features 效果最佳。不仅有 roadmaps（下图），IDE 还直接 set 好了每个场景。

enjoy~

New to me: Debugger

一直没认真学过如何 debug，当时我的 programming 101 是用 JavaScript，授课老师大概说："程序是否正确应该仅由你的思考所决定，而不是靠 console.log 打印出的东西。浪费时间在 debugger 工具上，不如花时间想清楚。"

差不多四年过去了，回想他的话，其实需要一个 context，也是那个课程的理念：「重要的是编程**，而不是工具。」有多少初学者是看到那复杂的 IDE 界面而放弃？

而对于 pro 来说，debugger just make life easier. 我写 Python 时，就很喜欢用 IPython.embed 当 breakpoint 查看手上 object 的 data structure，以及它的 method 用起来是怎样的；在写自动化程序（RPA）时就更好玩了，可以做到像在 REPL 控制 browser。

最后，Let's show off（对应教程的 Debug workflow）：

1. breakpoint 让程序停在你觉得出错的地方
2. evaluate 那个 expression 看是否真的出错了
3. 啊？真有出错，那就给这个 expression 加上 Watches，它会展示每一个变量
4. 接着自信地 Step Into，再 evaluate 每段觉得出错的 expression，并修改代码
5. 改好了吧，别急着 rerun！你甚至不需要重启 runtime，而是
   a. 按 Build，IDE 会自动 Patch 最新的 code
   b. 再按 Drop Frame 让 call stack 退回到 breakpoint，换言之就是 undo step 4.
6. resume program，相信一切顺利了

第五步对我来说很新鲜：）而整个 workflow 也是很好的实践。

Leetcode Top 100 Liked Questions

• 1. Two Sum
• 2. Add Two Numbers
• 3. Longest Substring Without Repeating Characters
• 4. Median of Two Sorted Arrays
• 5. Longest Palindromic Substring
• 10. Regular Expression Matching
• 11. Container With Most Water
• 15. 3Sum
• 17. Letter Combinations of a Phone Number
• 19. Remove Nth Node From End of List
• 20. Valid Parentheses
• 21. Merge Two Sorted Lists
• 22. Generate Parentheses
• 23. Merge k Sorted Lists
• 24. Swap Nodes in Pairs
• 25. Reverse Nodes in k-Group
• 31. Next Permutation
• 32. Longest Valid Parentheses
• 33. Search in Rotated Sorted Array
• 34. Find First and Last Position of Element in Sorted Array
• 35. Search Insert Position
• 39. Combination Sum
• 41. First Missing Positive
• 42. Trapping Rain Water
• 45. Jump Game II
• 46. Permutations
• 48. Rotate Image
• 49. Group Anagrams
• 53. Maximum Subarray
• 55. Jump Game
• 56. Merge Intervals
• 62. Unique Paths
• 64. Minimum Path Sum
• 70. Climbing Stairs
• 72. Edit Distance
• 74. Search a 2D Matrix
• 75. Sort Colors
• 76. Minimum Window Substring
• 78. Subsets
• 79. Word Search
• 84. Largest Rectangle in Histogram
• 85. Maximal Rectangle
• 94. Binary Tree Inorder Traversal
• 96. Unique Binary Search Trees
• 98. Validate Binary Search Tree
• 101. Symmetric Tree
• 102. Binary Tree Level Order Traversal
• 104. Maximum Depth of Binary Tree
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 114. Flatten Binary Tree to Linked List
• 121. Best Time to Buy and Sell Stock
• 124. Binary Tree Maximum Path Sum
• 127. Word Ladder
• 128. Longest Consecutive Sequence
• 131. Palindrome Partitioning
• 136. Single Number
• 138. Copy List with Random Pointer
• 139. Word Break
• 141. Linked List Cycle
• 142. Linked List Cycle II
• 146. LRU Cache
• 148. Sort List
• 152. Maximum Product Subarray
• 155. Min Stack
• 160. Intersection of Two Linked Lists
• 169. Majority Element
• 189. Rotate Array
• 198. House Robber
• 200. Number of Islands
• 206. Reverse Linked List
• 207. Course Schedule
• 208. Implement Trie (Prefix Tree)
• 210. Course Schedule II
• 215. Kth Largest Element in an Array
• 221. Maximal Square
• 226. Invert Binary Tree
• 234. Palindrome Linked List
• 236. Lowest Common Ancestor of a Binary Tree
• 238. Product of Array Except Self
• 239. Sliding Window Maximum
• 240. Search a 2D Matrix II
• 279. Perfect Squares
• 283. Move Zeroes
• 287. Find the Duplicate Number
• 295. Find Median from Data Stream
• 297. Serialize and Deserialize Binary Tree
• 300. Longest Increasing Subsequence
• 322. Coin Change
• 338. Counting Bits
• 347. Top K Frequent Elements
• 394. Decode String
• 416. Partition Equal Subset Sum
• 437. Path Sum III
• 438. Find All Anagrams in a String
• 494. Target Sum
• 543. Diameter of Binary Tree
• 560. Subarray Sum Equals K
• 617. Merge Two Binary Trees
• 739. Daily Temperatures
• 763. Partition Labels

Redux 用到了一个叫 Thunk 的词让我感兴趣，第一次看到这个词是在 SICP，于是想看看在这儿，它是干嘛的。四五个小时过去，我有如下收获...

学习资料

学会使用 Redux:

• If immutable objects are good, why do people keep creating mutable objects?
• Redux core concepts: https://redux.js.org/introduction/core-concepts
• Redux terms: https://redux.js.org/tutorials/essentials/part-1-overview-concepts#redux-terms-and-concepts
• Redux-middleware: https://redux.js.org/tutorials/fundamentals/part-4-store#writing-custom-middleware
• Redux-thunk: https://www.reddit.com/r/reactjs/comments/6e0vgt/is_my_understanding_of_reduxthunk_correct/

学会 Redux 的实现:

• Redux: https://blog.jakoblind.no/learn-redux-by-coding-a-mini-redux/
• Redux-thunk: https://blog.jakoblind.no/async-actions-with-redux-thunk-demystified/
• Redux-middleware: https://gist.github.com/shanehh/e0f89b38bc8ec0253900823c719eb881

上面的 blog 没有 Redux Middleware 的实现。我以前看过几篇 blog 实现 Express.js/Go Gin 的 middleware，回看觉得弄得复杂了点，recursion 写得像 iteration. 于是写了一个自认为 useless while elegant & powerful 的例子😁

看文档不开心的地方

对，我要抱怨一句，Redux 的示例代码风格对我来说还是太 smart 了一点。文档里的 Basic Example ，如果是我的话，就会把

function counter(state = 0, action) {
  switch (action.type) {
    case "INCREMENT":
      return state + 1
    case "DECREMENT":
      return state - 1
    default:
      return state
  }
}

let store = createStore(counter)

改成

function counter(state, action) {
  switch (action.type) {
    case "INCREMENT":
      return state + 1
    case "DECREMENT":
      return state - 1
    default:
      return state
  }
}

let store = createStore(counter, 0)