Make a Hash

Many data types and structures exist – from simple strings and integers to multi-dimensional arrays. One of the most common and useful types is the simple growable array that can contain an arbitrary number of elements. You can basically put data in, look it up, and remove it as needed; this structure is also referred to as a one-dimensional array. Often, you can also insert an array as a data element into an existing array, giving you a multi-dimensional array that lets you do things like create a "customer" array with a number of elements containing a customer name, phone number, and so forth.

About Arrays

Arrays typically have three major operations: insertion (adding elements), lookups (reading a value), and removing elements. There are a number of ways to structure the data in memory, and various strategies can be used to optimize operations on the array. A simple linked list, for example, makes it easy to add an element to the beginning or end of an array but expensive to insert an item into the middle, because it must search the array for the appropriate location. In general, most programming languages that provide well-formed data array structures, such as Perl, Python, Ruby, and so forth, do a pretty good job.

The most common strategy is to create a key based on the data (essentially a hash value), the array is then ordered by these keys. A significant benefit here is that the keys will (usually) have a random and relatively uniform distribution (e.g., 01, 23, 45, 67, 89). This approach is helpful when using things like binary trees, which benefit from having balanced key distribution. This is also referred to as a hash map.

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