Longest Substring Without Repeating Characters (LeetCode 3)

Given a string, find the length of the longest substring without repeating characters.

Syntactic Parsing Note (SLP Ch13)

This chapter focuses on the structures assigned by context-free grammars. Context-free grammars don’t specify how the parse tree for a given sentence should be computed. We therefore need to specify algorithms that employ these grammars to efficiently produce correct trees. They are useful in applications such as grammar checking, semantic analysis, question answering and information extraction.

Formal Grammars of English Note (SLP Ch12)

This chapter is devoted to the topic of context-free grammars. They are integral to many computational applications, including grammar checking, semantic interpretation, dialogue understanding, and machine translation.

信息熵与选择：由三门问题想到的

今天看公众号文章正好看到一篇《三门问题》，虽然看似简单，但细想感觉很有意思，特意把自己的思考记录一下。三门问题出自上世纪 70 年代美国的一个综艺节目，基本描述是这样的：你是游戏的参与者，面前有三扇门，其中一扇门后面是一辆跑车，其他两扇后面什么都没有。在你选择一扇门后先不打开，主持人打开了另一扇门（后面必然是空的），此时你有两个选择，坚持选择刚才选的那扇，或者换另外一扇还没打开的。怎么选择才能让你得到跑车的概率最大？

Sequence Processing with Recurrent Networks Note (SLP Ch09)

Problematic of the sliding window in general NN:

Like Markov it limits the context from which information can be extracted (limits to window area)
Window makes it difficult to learn systematic patterns arising from phenomena like constituency

RNN is a class of networks designed to address these problems by processing sequences explicitly as sequences, allowing us to handle variable length inputs without the use of arbitrary fixed-sized windows.

Part-of-Speech Tagging Note (SLP Ch08)

Parts-of-speech (also known as POS, word classes, or syntactic categories) are useful because they reveal a lot about a word and its neighbors. Useful for:

labeling named entities
coreference resolution
speech recognition or synthesis

一些关于工作的观点（From《华为工作法》）

武夷山旅途期间花了 3 个小时阅读了这本书，虽然本书以观念为主，且部分观点间界限比较模糊甚至有冲突，但却挺对自己的胃口，我一直也想让自己能像书中观点所说的那样工作，所以就整理了一下以便时常查阅。

Units

$z = w · x + b$

$y = \sigma(z) = \frac{1}{1+e^{-z}}$

In practice, the sigmoid is not commonly used as an activation function. A better one is tanh function ranges from -1 to 1: $$y = \frac{e^z - e^{-z}}{e^z + e^{-z}}$$

The most commonly used is the rectified linear unit, also called ReLU: y = max(x, 0)

In the sigmoid or tanh functions, very high values of z result in values of y that are saturated, extremely close to 1, which causes problems for learning.

Rectifiers don’t have this problem, since the output of values close to 1 also approaches 1 in a nice gentle linear way.
By contrast, the tanh function has the nice properties of being smoothly differentiable and mapping outlier values toward the mean.

长琴

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