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Enum std.range.SearchPolicy
Policy used with the searching primitives lowerBound
, upperBound
, and equalRange
of SortedRange
below.
enum SearchPolicy
: int { ... }
Enum members
Name | Description |
---|---|
binarySearch
|
Searches using a classic interval halving policy. The search
starts in the middle of the range, and each search step cuts
the range in half. This policy finds a value in Ο(log(n) )
time but is less cache friendly than gallop for large
ranges. The binarySearch policy is used as the last step
of trot , gallop , trotBackwards , and gallopBackwards strategies.
|
gallop
|
Performs a galloping search algorithm, i.e. searches
with a step that doubles every time, (1, 2, 4, 8, ...) leading
to an exponential search schedule (indexes tried are 0, 1, 3,
7, 15, 31, 63,...) Once the search overshoots its target, the
remaining interval is searched using binary search. A value is
found in Ο(log(n) ) time.
|
gallopBackwards
|
Similar to gallop but starts backwards. Use it when
confident that the value is around the end of the range.
|
linear
|
Searches in a linear fashion. |
trot
|
Searches with a step that is grows linearly (1, 2, 3,...)
leading to a quadratic search schedule (indexes tried are 0, 1,
3, 6, 10, 15, 21, 28,...) Once the search overshoots its target,
the remaining interval is searched using binary search. The
search is completed in Ο(sqrt(n) ) time. Use it when you
are reasonably confident that the value is around the beginning
of the range.
|
trotBackwards
|
Similar to trot but starts backwards. Use it when
confident that the value is around the end of the range.
|
Example
import std .algorithm .comparison : equal;
auto a = assumeSorted([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
auto p1 = a .upperBound!(SearchPolicy .binarySearch)(3);
assert(p1 .equal([4, 5, 6, 7, 8, 9]));
auto p2 = a .lowerBound!(SearchPolicy .gallop)(4);
assert(p2 .equal([0, 1, 2, 3]));
Authors
Andrei Alexandrescu, David Simcha, Jonathan M Davis, and Jack Stouffer. Credit for some of the ideas in building this module goes to Leonardo Maffi.
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.