# Binary Search in Delphi Pascal

#### Implement a binary search algorithm.

1 | ```
exercism fetch delphi binary-search
``` |

# Binary Search

Implement a binary search algorithm.

Searching a sorted collection is a common task. A dictionary is a sorted list of word definitions. Given a word, one can find its definition. A telephone book is a sorted list of people's names, addresses, and telephone numbers. Knowing someone's name allows one to quickly find their telephone number and address.

If the list to be searched contains more than a few items (a dozen, say) a binary search will require far fewer comparisons than a linear search, but it imposes the requirement that the list be sorted.

In computer science, a binary search or half-interval search algorithm finds the position of a specified input value (the search "key") within an array sorted by key value.

In each step, the algorithm compares the search key value with the key value of the middle element of the array.

If the keys match, then a matching element has been found and its index, or position, is returned.

Otherwise, if the search key is less than the middle element's key, then the algorithm repeats its action on the sub-array to the left of the middle element or, if the search key is greater, on the sub-array to the right.

If the remaining array to be searched is empty, then the key cannot be found in the array and a special "not found" indication is returned.

A binary search halves the number of items to check with each iteration, so locating an item (or determining its absence) takes logarithmic time. A binary search is a dichotomic divide and conquer search algorithm.

## Testing

In order to run the tests for this track, you will need to install DUnitX. Please see the installation instructions for more information.

### Loading Exercises into Delphi

If Delphi is properly installed, and `*.dpr`

file types have been associated with Delphi, then double clicking the supplied `*.dpr`

file will start Delphi and load the exercise/project. `control + F9`

is the keyboard shortcut to compile the project or pressing `F9`

will compile and run the project.

Alternatively you may opt to start Delphi and load your project via. the `File`

drop down menu.

### When Questions Come Up

We monitor the Pascal-Delphi support room on gitter.im to help you with any questions that might arise.

### Submitting Exercises

Note that, when trying to submit an exercise, make sure the exercise file you're submitting is in the `exercism/delphi/<exerciseName>`

directory.

For example, if you're submitting `ubob.pas`

for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/delphi/bob/ubob.pas`

.

## Source

Wikipedia http://en.wikipedia.org/wiki/Binary_search_algorithm

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.