std::experimental:: sample
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Defined in header
<experimental/algorithm>
|
||
|
template
<
class
PopulationIterator,
class
SampleIterator,
class
Distance,
class
URBG
>
|
(1) | (library fundamentals TS) |
|
template
<
class
PopulationIterator,
class
SampleIterator,
class
Distance
>
SampleIterator sample
(
PopulationIterator first, PopulationIterator last,
|
(2) | (library fundamentals TS v2) |
Selects
n
elements from the sequence
[
first
,
last
)
such that each possible sample has equal probability of appearance, and writes those selected elements into the output iterator
out
.
If n is greater than the number of elements in the sequence, selects last - first elements.
The algorithm is stable only if
PopulationIterator
meets the requirements of
LegacyForwardIterator
.
Parameters
| first, last | - | pair of iterators forming the range from which to make the sampling (the population) |
| out | - |
the output iterator where the samples are written. Must not be in the range
[
first
,
last
)
|
| n | - | number of samples to make |
| g | - | the random number generator used as the source of randomness |
-
PopulationIterator
must meet the requirements of
LegacyInputIterator
.
|
||
-
SampleIterator
must meet the requirements of
LegacyOutputIterator
.
|
||
-
SampleIterator
must also meet the requirements of
LegacyRandomAccessIterator
if
PopulationIterator
doesn't meet
LegacyForwardIterator
.
|
||
-
PopulationIterator
's value type must be writeable to
out
.
|
||
-
Distance
must be an integer type.
|
||
-
URBG
must meet the requirements of
UniformRandomBitGenerator
and its return type must be convertible to
Distance
.
|
||
Return value
Returns a copy of out after the last sample that was output, that is, end of the sample range.
Complexity
Linear in std:: distance ( first, last ) .
Notes
This function may implement selection sampling or reservoir sampling.
Example
#include <experimental/algorithm> #include <iostream> #include <iterator> #include <random> #include <string> int main() { std::string in = "abcdefgh", out; std::experimental::sample(in.begin(), in.end(), std::back_inserter(out), 5, std::mt19937{std::random_device{}()}); std::cout << "five random letters out of " << in << " : " << out << '\n'; }
Possible output:
five random letters out of abcdefgh : cdefg
See also
|
(until C++17)
(C++11)
|
randomly re-orders elements in a range
(function template) |