All Questions

4312
votes
33answers
572180 views

What is a plain English explanation of "Big O" notation?

I'd prefer as little formal definition as possible and simple mathematics.
1127
votes
16answers
144420 views

What is the best algorithm for an overridden System.Object.GetHashCode?

In .NET System.Object.GetHashCode method is used in a lot of places, throughout the .NET base class libraries. Especially when finding items in a collection fast or to determine equality. Is there a ...
480
votes
64answers
368636 views

Algorithm to return all combinations of k elements from n

I want to write a function that takes an array of letters as an argument and a number of those letters to select. Say you provide an array of 8 letters and want to select 3 letters from that. Then y...
703
votes
49answers
449058 views

How to count the number of set bits in a 32-bit integer?

8 bits representing the number 7 look like this: 00000111 Three bits are set. What are algorithms to determine the number of set bits in a 32-bit integer?
409
votes
25answers
283873 views

What is the most effective way for float and double comparison?

What would be the most efficient way to compare two double or two float values? Simply doing this is not correct: bool CompareDoubles1 (double A, double B) { return A == B; } But something like...
640
votes
33answers
516600 views

Calculate distance between two latitude-longitude points? (Haversine formula)

How do I calculate the distance between two points specified by latitude and longitude? For clarification, I'd like the distance in kilometers; the points use the WGS84 system and I'd like to underst...
443
votes
14answers
89014 views

What is the most efficient/elegant way to parse a flat table into a tree?

Assume you have a flat table that stores an ordered tree hierarchy: Id Name ParentId Order 1 'Node 1' 0 10 2 'Node 1.1' 1 10 3 'Node 2' 0...
738
votes
22answers
341206 views

Big O, how do you calculate/approximate it?

Most people with a degree in CS will certainly know what Big O stands for. It helps us to measure how (in)efficient an algorithm really is and if you know in what category the problem you are trying t...
380
votes
26answers
382678 views

How to generate all permutations of a list in Python

How do you generate all the permutations of a list in Python, independently of the type of elements in that list? For example: permutations([]) [] permutations([1]) [1] permutations([1, 2]) [1, 2]...
608
votes
10answers
413314 views

How to find time complexity of an algorithm

The Question How to find time complexity of an algorithm? What have I done before posting a question on SO ? I have gone through this, this and many other links But no where I was able to find a c...

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