三个月内看完CLRS，伪码实现大部分。(持续整理 7/3)

由 https://www.cnblogs.com/clemente/p/9902220.html 整理得到，内容会有所不同，侵删。

Chapter 1

Interesting read, but you can skip it.

Chapter 2

2.1 Insertion Sort - To be honest you should probably know all major sorting algorithms, not just insertion sort. It’s just basic knowledge and you never know when it can help.
2.2 Analysis of Algorithms - you can skip the small intro, but know the rest.
2.3 Designing algorithms - contains merge sort and its analysis as well as an overview of divide-and-conquer, very important stuff, so worth a read.

Chapter 3

All of it. You have to know big-O notation and time complexity analysis, period.Chapter 44.1 Maximum
subarray problem - Can kind of be worth your time. There are better
solutions to this problem than divide and conquer but it’s good practice
and the flow of logic may help develop how you think.4.2 Strassen’s
algorithm - I really love this algorithm and was astounded at how cool
it was the first time I saw it, but you can skip it for the interviews.
It won’t come up.4.3 Substitution method - you won’t be using
this method in an interview, but you should know it since it’s a basic
tool for finding the time complexity of a recursive algorithm.4.4 Recurrence tree method - same as 4.34.5 Master
method - essential knowledge. You should know it and practice with it
and be able to use it in 3 seconds. This is the method you would use in
an interview if analyzing a recursive algorithm that fits the form.4.6 Proof
of the master theorem - you can probably skip this, though it’s good to
read at least once so that you understand what you’re doing with the
master method.Chapter 5I’ve never read this chapter, to
be honest, but what I know is that you need a basic grasp of
probability in interviews because there’s a good chance they may come
up. That said, as long as you know basic probability concepts and
practice on probability-related interview problems (there are such
problems with solution explanations in Elements of Programming Interviews,
the book I recommend for interview prep), you can probably skip this
chapter. From a cursory glance, it’s more math than algorithms.Chapter 66.1, 6.2, 6.3, 6.4, 6.5 - Heaps and heapsort. Check.Chapter 77.1, 7.2, 7.3 - Quicksort
and its randomized version. Need-to-know concepts. I also recommend 7.4
(I was once asked in an interview to high-level-analyze a randomized
algorithm), though the probability you have to deal with something like
7.4 in an interview is pretty low, I’d guess.Chapter 88.1 - Lower
bounds on sorting - Yes. Basic knowledge. May be asked in a Google
interview (though unlikely, I know of a case it happened in before).8.2 - Counting sort - Need-to-know in detail. It comes up in disguised forms.8.3 - Radix sort - Yup. It’s an easy algorithm anyway.8.4 - Bucket sort - can skip.Chapter 99.1 - Small section, worth a read.9.2 - Selection in expected linear time - Very important,
as it’s not common knowledge like quicksort and yet it comes up often
in interviews. I had to code the entire thing in an interview once.9.3 - Selection
in worst-case linear time - Can skip. Just know that it’s possible in
worst-case linear time, because that might help somewhat.Chapter 1010.1 - Stacks and queues - basic knowledge, definitely very important.10.2 - Linked lists - same as 10.110.3 - Implementing pointers and objects - If you use C++ or Java, skip this. Otherwise I’m not sure.10.4 - Representing rooted trees - Small section, worth a quick read.Chapter 11For
hashing, I’d say the implementation isn’t as important to know as, for
example, linked lists, but you should definitely have an idea about it
and most importantly know the (expected and worst-case) time
complexities of search/insert/delete etc. Also know that practically,
they’re very important data structures and, also practically, the
expected time complexity is what matters in the real world.11.1 - Direct addressing - Just understand the idea.11.2 - Hash tables - important.11.3 - Hash
functions - it’s worth having an idea about them, but I wouldn’t go too
in-depth here. Just know a couple examples of good and bad hash
functions (and why they are good/bad).11.4 - Open addressing - Worth having an idea about, but unlikely to come up.11.5 - Perfect hashing - skip. Chapter 1212.1 - What is a binary search tree? - Yep.12.2 - Querying a BST - Yep. All of it.12.3 - Insertion/Deletion - Same as 12.212.4 - Randomly built BSTs - just know Theorem 12.4 (expected height of random BST is O(lgn)) and an idea of why it’s true.Chapter 13This one is easy. Know what a Red-Black tree is, and what its worst-case height/insert/delete/find are. Read 13.1 and 13.2,
and skip the rest. You will never be asked for RB-tree insert/delete
unless the interviewer is “doing it wrong”, or if the interviewer wants
to see if you can re-derive the cases, in which case knowing them won’t
help much anyway (and I doubt this would happen anyway). Also know that
RB-trees are pretty space-efficient and some C++ STL containers are
built as RB-trees usually (e.g. map/set).Chapter 14Might be worth skimming 14.2 just
to know that you can augment data structures and why it might be
helpful. Otherwise do one or two simple problems on augmenting data
structures and you’re set here. I’d skip 14.1 and 14.3.Chapter 15DP! Must-know.15.1 - Rod-cutting. Standard DP problem, must-know.15.2 - Matrix-chain
multiplication - same as 15.1, though I don’t particularly like the way
this section is written (it’s rare for me to say that about CLRS).15.3 - Elements
of DP - worth a read so that you understand DP properly, but I’d say
it’s less important than knowing what DP is (via the chapter
introduction) and practicing on it (via the problems in this book and in
interview preparation books).15.4 - LCS - same as 15.115.5 - Optimal binary search trees - I’ve never read this section, so I can’t argue for its importance, but I did fine without it.Chapter 16You should definitely know what a greedy algorithm is, so read the introduction for this chapter.16.1 - An activity selection problem - Haven’t read this in detail, but I’d say check it out, if not in-depth.16.2 - Elements of the greedy strategy - same as 16.116.3 - Huffman
codes - I’d say read the problem and the algorithm, but that’s enough.
I’ve seen interview questions where the answer is Huffman coding (but
the question will come up in a ‘disguised form’, so it won’t be
obvious.)16.4 - Matroids and greedy methods - I’ve never read
this section, but I’ve done a lot of greedy problems during interview
prep and this stuff never came up, so I’d say this section is irrelevant
for the interview.16.5 - Task-scheduling problem as a matroid - Same as 16.4.Chapter 17Okay,
you should definitely know what amortized analysis is, but I’ve never
read it from the book and I feel it’s a sufficiently simple concept that
you can just Google it and check a few examples on what it is, or
understand it just by reading section 17.1. So:17.1 - Aggregate analysis - read this, it explains the important stuff.17.2, 17.3, 17.4 - Skip.Chapter 18You
should probably have an idea of what B-Trees (and B+ trees) are, I’ve
heard of cases where candidates were asked about them in a general sense
(high-level questions about what they are and why they’re awesome). But
other than that I’d skip this chapter.Chapter 19Fibonacci heaps - nope.Chapter 20van Emde Boas Trees - double, triple, and quadruple nope.Chapter 21Disjoint setsUpdate:
I originally recommended skipping this section, but on reconsideration,
I’ve noticed that it’s actually more important than I originally
thought. Thus, I recommend reading sections 21.1 and 21.2, while skipping the rest.Union-find
is somewhat important and I’ve seen at least one problem which uses it,
though that problem could also be solved using DFS and connected
components. That said, I also believe that it’s not strictly necessary
because one can probably, for interview purposes, come up with a similar
enough structure easily to solve a problem which requires union-find,
without knowing the material in this chapter. However, I believe it’s
worth a read so that if a problem comes up whose intended solution is a
union-find data structure, you don’t spend time in an interview coming
up with it, and rather know from before, which can be a good advantage.
Still, I’d probably rank it as less important than most of the other
material in this list, and even less than other material that’s not even
in CLRS (like tries, for example).Okay, now graph algorithms. First read the introduction. Now, there’s a lot to know here, so hang on.Chapter 2222.1 - Representations of graphs - Yes.22.2 - BFS - Yes. After you do that, solve this problem: ACM-ICPC Live Archive - Kermit the Frog. The whole “state-space search using BFS” thing is an important concept that might be used to solve several interview problems.22.3 - DFS - Yes.22.4 - Topological sort - Yes.22.5 - Strongly connected components - much less likely to come up than the above 4, but still possible, so: Yes.Chapter 23Minimum
spanning trees - probably the least important graph algorithm, other
than max flow (I mean for interview purposes, of course). I’d still say
you should read it because it’s such a well-known problem, but
definitely give priority to the other things.23.1 - Growing a MST - sort of, yes.23.2 - Prim and Kruskal’s algorithms - sort of, yes.Chapter 24Shortest path algorithms are important, though maybe less so than BFS/DFS.Read
the introduction. You should, in general, read all introductions
anyway, but this one’s important (and long), so it warranted a special
note.24.1 Bellman-Ford - Know the algorithm and its proof of correctness.24.2 Shortest paths in DAGs - definitely worth knowing, may come up, even more so than Bellman-Ford I’d say.24.3 Dijkstra’s
algorithm - Yes. Of course. I’ve seen this come up multiple times (with
slight variations), and I’ve even seen A* come up.24.4 Difference constraints and shortest paths - Skip.Chapter 25Read the intro as well.25.1 - Matrix multiplication -I’d
say skip. It might be possible for this to come up (very very slim
chance that it does though), but the chances are so low in my view that
it’s probably not worth it. If you have some extra time, though, give it
a read.25.2 - Floyd-Warshall - Yep, worth knowing the
algorithm and its time complexity and when it works (which is for all
weighted graphs, except ones with negative weight cycles). Its code is
something like 5 lines so there’s no reason not to know it. The analysis
might be a bit overkill though.25.3 - Johnson’s algorithm - Skip.Chapter 26Maximum flow - I’ve never heard of this coming up in an interview and I can’t imagine why it would, so skip.Chapters 27+Most
of this stuff is never going to come up, so it’s easier for me to tell
you what to actually read than what not to read, so here are a few
selected topics from the Selected Topics in the book:Chapter 31Most
of what you should learn from this chapter you can learn from
practicing on interview problems from Elements of Programming Interviews
(and your time is better spent doing that), so I’d say skip it all
except Euclid’s algorithm for the GCD, under section 31.2.Chapter 3232.1 - Naive method - just read it quickly.32.2 - Rabin-Karp

• I’d say you should know this, the rolling hash concept is very
  important and can be useful in many string- or search-related interview
  problems.AppendicesA - SummationsKnow the important summations for time complexity analysis.C - Counting and ProbabilityGive C.4
  a read if you don’t know the material, Bernoulli trials may come up in
  problems (not explicitly, but you might use them, specifically for time
  analysis of questions that involve probability/coin flips).