Hello all,
I’ve been practicing at Codechef for a while and now I’m gradually moving toward medium/hard problems. However many algorithms at these levels are very difficult to predict, and I was always stuck because I’m not aware of them. So I open this topic, my hope is to have a wish-list of most used algorithm for online programming contest that I can look up for reference. Here is my short-list up to now:

Edit: It would be a nice idea to group these algorithms. For example, KMP algortihm, Aho-Corasick algorithm, Rabin-Karp algorithm all fall under the category of String Match, and hence should be put under the category of string match algorithms; and so on for other algorithms as well.

Grouping would help newbies like me to explore a particular group and learn all the algorithms in that.

Sadly, this list is endless and the hardest part is to understand which of these topics need to be applied to solve a given problem.
As a bonus, you can have variations of these standard topics which may require mixing some of these concepts.

I will edit the above post with all these suggestions, except some of the suggestions given by @n2n_, since putting on the same bag, FFT and Sieve of Eratosthenes for finding primes, seems a bit overkill to me, as the second one is a basic algorithm and not needed to advanced problems I would say

A very useful link ,list in-dept analysis of basic to advanced algorithm ,many which are listed above ,very helpful read MAXimal :: algo though in russian but google translator might help.

Is the idea of linking all of the above topics to some resource with a tutorial and suggested problems still up?

Because if it is, I can try to write about the topic 3. Fast Modulo Multiplication (Exponential Squaring), as it is a topic I master relatively well, and, when I’m finished with my tutorial I can provide the link here

This is not an algorithm. The way they can describe a lot of stuff is nice, but I’ve never ever seen them used in a solution in competitive programming (unless you count “bruteforce the first few numbers and google them in OEIS” an algorithm, which I don’t).

Similarly, anything that contains “ad-hoc” is not an algorithm, practically by definition. “Ad-hoc” means something that doesn’t fall under a well-known algorithmic technique.

There is an “awesome” resource for this and a lot other things. https://github.com/sindresorhus/awesome
Though I don’t remember the original author’s name, this is the best I’ve come across. Be sure to check it out.

You can also add data structures as DS + Algo’s = Programs. I suggest adding a few basic data structures which would help. Also you could add topics like DP.

Can anyone also mention the approaches that we have to know like Dynamic Programming or any other approaches for programming contests.
Classifying these algorithms based on the approach will also really be beneficial, may be i am asking for more here :).