Read Dynamic Programming and practiced 4 more dynamic programming algorithms
Read system design documents - How to design YouTube.
Spent 2 hours on HackerRank to do more code challenges.
1. Reading: 60 minutes - O
2. Side Project(s): 120 minutes - X
3. Code Practices: 120 minutes - O
4. Exercises: 30 minutes - O
House Democrats voted Friday to defend localities that allow illegal immigrants to vote in their elections, turning back a GOP attempt to discourage the practice. As The Washington Times reports, the vote marks a stunning reversal from just six months ago, when the chamber - then under GOP control - voted to decry illegal immigrant voting.
昨日阅读1小时。 总阅读时间137时
The business of value investing – Six essential elements to buying companies like Warren Buffett- Charlie Tian 2009
https://bbs.pinggu.org/thread-695143-1-1.html (Page 187-195)
Growing intrinsic value provides undervaluation
Conservative Tests of Safety a Must
阅读到的有价值的内容段落摘录
It cannot be stressed enough that discovering a business with future growth prospects selling at a reasonable price is only the first step in the investment process. Never, ever invest simply because such conditions exist. But if you do find them, you can go on to determine whether the business can sustain this growth for a period of years and whether this growth will require high levels of capital expenditures. As the company grows, so will intrinsic value and, ultimately, so will the market value. Even when sitting still, however, the investors’ work is not complete. On the contrary, once an investment is made, the work becomes more painstaking. Determining that a security is undervalued and suitable for purchase is one thing; ensuring that the business remains an attractive investment is quite another. At a minimum, investors should check on the status of the investment quarterly along with the required regulatory filings issued by the business to the Securities and Exchange Commission. The purpose of these regular check-ups is to be on the lookout for any significant signs that the overall fundamental condition of the business is deteriorating. Making such a determination is both part art and science. Generally, quarterly performance should be of no significant concern if the investment made truly satisfied the conditions of an undervalued one with a satisfactory margin of safety. Of course, careful detail and analysis should be given to the annual report, which lays out the results of the year and the future prospects of the company. In addition, investors should be well aware of the industry and competitive forces that might affect the investment. Doing all of this analysis will significantly increase the likelihood that the investment is disposed of when it reaches intrinsic value, which should result in a gain if the security was purchased at significantly below the intrinsic value. If not, then again, investors face a good possibility that the investment will be sold at a minimal loss.
Most of us are not old enough to recall the pain of the Great Depression, and some may not even remember the bear market of the early 1970s. Unfortunately, many were exposed to the severe market decline in 2008 as a result of decades of excessive borrowing in the United States. 5 The year 2008 managed to eclipse the 1973 bear in terms of total loss for a year: 38.5 percent for the S&P 500 index. Not since 1931, at the height of the Great Depression, has a market lost so much in a single year. The severe economic recession that took hold in 2008 highlights the need for conservative tests for safety when analysing investments. Going a step further, 2008 illustrated the need for investors to analyze companies under the severest of operating conditions. No longer was it satisfactory to assess future intrinsic values based on earning results of the past several years.
阅读到的有价值信息的自我思考点评感想
In times many companies likely will be earning record profits as severe economic conditions force out weaker, less efficient competitors. The market collapse of 2008 simply reinforces the absolute requirement for a margin of safety that can pass the test during prolonged periods of economic contraction. In the case of DryShips, it was absolutely necessary to re-evaluate the carrying costs of the assets in light of reduced valuations for the vessels. Simply assigning the stated book value of 49 a share was not satisfactory in order to assign a conservative book value for the company. In the case of Johnson & Johnson, over 100 years of profitability during various economic conditions was in itself a satisfactory condition that the company was still a suitable investment.
Investment in stocks should be made with a long - term orientation. In the short run, market prices are affected by the votes of the market participants. In the long run, stock prices will catch up with the fundamentals of the business. Along with reduced trading mistakes, a patient investment approach minimizes transaction costs. The level of cash in a portfolio should be affected by the availability of bargain investments. Some of the markets’ greatest benefits— liquidity and establishment of prices can also be a source of great loss to investors who fall prey to the unnecessary noise they often create. General undervalued investments arise from two situations: market prices below private sale value or buying growth businesses at reasonable prices. Both situations allow for an investment to be made at prices sufficiently below intrinsic value.
The baffling quantum maths solution it took 10 years to understand
A FEW corners of the internet still rock something of a 1998 vibe, and Princeton University’s server has one of them. The text is in Times New Roman and comes in clashing shades of red, blue, mauve and orange. Down the left side is a list of seemingly obscure phrases like “Impossibility theorems”, “Spin glass” and “Separatrix separation”.
This is the website for Open Problems in Mathematical Physics, which, as the name suggests, is a list of the most mind-bending unsolved maths conundrums in physics. Crack any one of these beasts and you would probably earn yourself a Fields medal, the maths equivalent of a Nobel prize. That, and the editor of the website will post a cartoon explosion next to the problem bearing the word SOLVED!
One of these problems has had mathematicians stumped for years, with legions of them having made only piecemeal progress. Few people outside physics have heard of the quantum Hall conductance problem, but it is intimately connected with experiments that get us closer than ever to harnessing the mysterious power of quantum technology. You can imagine the anticipation, then, when a newcomer named Spyridon Michalakis claimed he had the answer. Fittingly, however, his solution to this impossible problem was itself impossible to understand – or at least nearly impossible.
在物理学界之外，很少有人听说过量子霍尔电导问题（quantum Hall conductance problem），但它与量子技术的实际应用有着紧密关系。你可以想象，当一位名为Spyridon Michalakis的新人声称得到了答案时，人们作何期望。然而，他提出的这个“不可能问题”的解法本身就不可能被理解——或说，是差点不可能。
霍尔的发现比电子被发现还要早18年。1980年物理学家冯·克利青（Klaus von Klitzing）的重复实验确证了这一效应，这次电流通过的是冷却到接近绝对零度的金属和半导体之间的薄界面。在这些条件下，电流是二维的，正如超薄石墨烯材料一样，二维完全改变了它的性质。冯·克利青发现，如果缓慢增加磁场强度，偏转的电流并不会像预期般稳定增长，而是发生阶跃。
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