std::experimental::sample
<experimental/algorithm>
class Distance, class URBG >
SampleIterator sample( PopulationIterator first, PopulationIterator last,
SampleIterator out, Distance n,
SampleIterator sample( PopulationIterator first, PopulationIterator last,
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.
[edit] Parameters
[first, last)
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.
[edit] Return value
Returns a copy of out after the last sample that was output, that is, end of the sample range.
[edit] Complexity
Linear in std::distance (first, last).
[edit] Notes
This function may implement selection sampling or reservoir sampling.
[edit] 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