std::nth_element
From Cppreference
| Defined in header <algorithm>
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| template< class RandomAccessIterator >
void nth_element( RandomAccessIterator first, |
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| template< class RandomAccessIterator, class Compare >
void nth_element( RandomAccessIterator first, |
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Partially sorts the range [first, last) in ascending order so that all elements in the range [first, nth) are less than those in the range [nth, last). The first version uses operator< to compare the elements, the second version uses the given comparison function comp. The element placed in the nth position is exactly the element that would occur in this position if the range was fully sorted.
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[edit] Parameters
| first, last | - | random access iterators defining the range sort | |||||||||
| nth | - | random access iterator defining the sort partition point | |||||||||
| comp | - | comparison function which returns true if the first argument is less than the second. The signature of the comparison function should be equivalent to the following:
The signature does not need to have const &, but the function must not modify the objects passed to it. |
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[edit] Return value
(none)
[edit] Complexity
Linear in std::distance(first, last) on average.
[edit] Example
#include <iostream> #include <vector> #include <algorithm> #include <functional> int main() { std::vector<int> v{5, 6, 4, 3, 2, 6, 7, 9, 3}; std::nth_element(v.begin(), v.begin() + v.size()/2, v.end()); std::cout << "The median is " << v[v.size()/2] << '\n'; std::nth_element(v.begin(), v.begin()+1, v.end(), std::greater<int>()); std::cout << "The second largest element is " << v[1] << '\n'; }
Output:
The median is 5 The second largest element is 7
[edit] See also
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copies and partially sorts a range of elements (function template) |
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sorts a range of elements while preserving order between equal elements (function template) |
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sorts a range into ascending order (function template) |
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