std::experimental::sample
| Defined in header <experimental/algorithm>
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| 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
g.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 [first;last) range |
| n | - | number of samples to make |
| g | - | the random number generator used as the source of randomness |
-PopulationIterator must meet the requirements of LegacyInputIterator.
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-SampleIterator must meet the requirements of LegacyOutputIterator.
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-SampleIterator must also meet the requirements of LegacyRandomAccessIterator if PopulationIterator doesn't meet LegacyForwardIterator
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-PopulationIterator's value type must be writeable to out
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-Distance must be an integer type
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-URBG must meet the requirements of UniformRandomBitGenerator and its return type must be convertible to Distance
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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 <iostream> #include <random> #include <string> #include <iterator> #include <experimental/algorithm> 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) |