54 lines
2.1 KiB
Markdown
54 lines
2.1 KiB
Markdown
# Binary Search
|
|
|
|
Write a program that implements 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.
|
|
|
|
To run the tests simply run the command `go test` in the exercise directory.
|
|
|
|
If the test suite contains benchmarks, you can run these with the `-bench`
|
|
flag:
|
|
|
|
go test -bench .
|
|
|
|
For more detailed info about the Go track see the [help
|
|
page](http://exercism.io/languages/go).
|
|
|
|
## Source
|
|
|
|
Wikipedia [http://en.wikipedia.org/wiki/Binary_search_algorithm](http://en.wikipedia.org/wiki/Binary_search_algorithm)
|
|
|
|
## Submitting Incomplete Problems
|
|
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
|
|
|