It is much harder to build components that use more than two states/levels/whatever. For example, the transistors used in logic are either closed and don’t conduct at all, or wide open. Having them half open would require much more precision and use extra power. Nevertheless, sometimes more states are used for packing more data, but … Read more
There is not only a Wikipedia article on graph isomorphism (as Space_C0wb0y points out) but also a dedicated article on the graph isomorphism problem. It has a section Solved special cases for which polynomial-time solutions are known. Trees is one of them and it cites the following two references: P.J. Kelly, “A congruence theorem for … Read more
Closures, lambdas, and anonymous functions are not necessarily the same thing. An anonymous function is any function that doesn’t have (or, at least, need) its own name. A closure is a function that can access variables that were in its lexical scope when it was declared, even after they have fallen out of scope. Anonymous … Read more
Take a look at this blog post by Steve Yegge (formerly of Amazon, now at Google): The Five Essential Phone Screen Questions It goes into some detail about the the five most important concepts that developers should be required to know: Basic programming (including recursion, file I/O, formatted output, loops etc) Object oriented design (including … Read more
A byte is 8 bits (binary data). A byte array is an array of bytes (tautology FTW!). You could use a byte array to store a collection of binary data, for example, the contents of a file. The downside to this is that the entire file contents must be loaded into memory. For large amounts … Read more
There are a number of good explanations of recursion in this thread, this answer is about why you shouldn’t use it in most languages.* In the majority of major imperative language implementations (i.e. every major implementation of C, C++, Basic, Python, Ruby,Java, and C#) iteration is vastly preferable to recursion. To see why, walk through … Read more
I would say that a checksum is necessarily a hashcode. However, not all hashcodes make good checksums. A checksum has a special purpose — it verifies or checks the integrity of data (some can go beyond that by allowing for error-correction). “Good” checksums are easy to compute, and can detect many types of data corruptions … Read more
When to use Pre-Order, In-Order, and Post-Order Traversal Strategy Before you can understand under what circumstances to use pre-order, in-order and post-order for a binary tree, you have to understand exactly how each traversal strategy works. Use the following tree as an example. The root of the tree is 7, the left most node is … Read more
Eventual consistency: I watch the weather report and learn that it’s going to rain tomorrow. I tell you that it’s going to rain tomorrow. Your neighbor tells his wife that it’s going to be sunny tomorrow. You tell your neighbor that it is going to rain tomorrow. Eventually, all of the servers (you, me, your … Read more