std::minmax
Defined in header <algorithm> |
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|---|---|---|
| (1) | ||
template< class T > std::pair<const T&,const T&> minmax( const T& a, const T& b ); |
(since C++11) (until C++14) |
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template< class T > constexpr std::pair<const T&,const T&> minmax( const T& a, const T& b ); |
(since C++14) | |
| (2) | ||
template< class T, class Compare >
std::pair<const T&,const T&> minmax( const T& a, const T& b,
Compare comp ); |
(since C++11) (until C++14) |
|
template< class T, class Compare >
constexpr std::pair<const T&,const T&> minmax( const T& a, const T& b,
Compare comp ); |
(since C++14) | |
| (3) | ||
template< class T > std::pair<T,T> minmax( std::initializer_list<T> ilist); |
(since C++11) (until C++14) |
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template< class T > constexpr std::pair<T,T> minmax( std::initializer_list<T> ilist); |
(since C++14) | |
| (4) | ||
template< class T, class Compare > std::pair<T,T> minmax( std::initializer_list<T> ilist, Compare comp ); |
(since C++11) (until C++14) |
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template< class T, class Compare > constexpr std::pair<T,T> minmax( std::initializer_list<T> ilist, Compare comp ); |
(since C++14) |
Returns the lowest and the greatest of the given values.
a and
b.
ilist.
The (1,3) versions use operator< to compare the values, whereas the (2,4) versions use the given comparison function comp.
Parameters
| a, b | - | the values to compare |
| ilist | - | initializer list with the values to compare |
| comp | - | comparison function object (i.e. an object that satisfies the requirements of Compare) which returns true if the first argument is less than the second. The signature of the comparison function should be equivalent to the following:
While the signature does not need to have |
| Type requirements | ||
-T must meet the requirements of LessThanComparable in order to use overloads (1,3). |
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-T must meet the requirements of CopyConstructible in order to use overloads (3,4). |
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Return value
std::pair<const T&, const T&>(a, b) if
a<b or if
a is equivalent to
b. Returns the result of
std::pair<const T&, const T&>(b, a) if
b<a.
ilist as the first element and the greatest as the second. If several elements are equivalent to the smallest, the leftmost such element is returned. If several elements are equivalent to the largest, the rightmost such element is returned.
Complexity
ilist.size() * 3 / 2 comparisons
Possible implementation
| First version |
|---|
template<class T>
constexpr std::pair<const T&, const T&> minmax( const T& a, const T& b )
{
return (b < a) ? std::pair<const T&, const T&>(b, a)
: std::pair<const T&, const T&>(a, b);
}
|
| Second version |
template<class T, class Compare>
constexpr std::pair<const T&, const T&> minmax( const T& a, const T& b, Compare comp )
{
return comp(b, a) ? std::pair<const T&, const T&>(b, a)
: std::pair<const T&, const T&>(a, b);
}
|
| Third version |
template< class T >
constexpr std::pair<T, T> minmax( std::initializer_list<T> ilist )
{
auto p = std::minmax_element(ilist.begin(), ilist.end());
return std::pair(*p.first, *p.second);
}
|
| Fourth version |
template< class T, class Compare >
constexpr std::pair<T, T> minmax( std::initializer_list<T> ilist, Compare comp )
{
auto p = std::minmax_element(ilist.begin(), ilist.end(), comp);
return std::pair(*p.first, *p.second);
}
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Notes
For overloads (1,2), if one of the parameters is a temporary, the reference returned becomes a dangling reference at the end of the full expression that contains the call to minmax:
int n = 1; auto p = std::minmax(n, n+1); int m = p.first; // ok int x = p.second; // undefined behavior // Note that structured bindings have the same issue auto [mm, xx] = std::minmax(n, n+1); xx; // undefined behavior
Example
#include <algorithm>
#include <iostream>
#include <vector>
#include <cstdlib>
#include <ctime>
int main()
{
std::vector<int> v {3, 1, 4, 1, 5, 9, 2, 6};
std::srand(std::time(0));
std::pair<int, int> bounds = std::minmax(std::rand() % v.size(),
std::rand() % v.size());
std::cout << "v[" << bounds.first << "," << bounds.second << "]: ";
for (int i = bounds.first; i < bounds.second; ++i) {
std::cout << v[i] << ' ';
}
std::cout << '\n';
}
Possible output:
v[2,7]: 4 1 5 9 2
See also
| returns the smaller of the given values (function template) |
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| returns the greater of the given values (function template) |
|
|
(C++11)
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returns the smallest and the largest elements in a range (function template) |
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(C++20)
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returns the smaller and larger of two elements (niebloid) |
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