template< class T >
std::pair <const T&, const T&> minmax( const T& a, const T& b );
(1)
(since C++11) (constexpr since C++14)
template< class T, class Compare >
std::pair <const T&, const T&> minmax( const T& a, const T& b,
Compare comp );
(2)
(since C++11) (constexpr since C++14)
(3)
(since C++11) (constexpr since C++14)
(4)
(since C++11) (constexpr since C++14)
Returns the lowest and the greatest of the given values.
1,2) Returns references to the smaller and the greater of a and b.
1) Uses operator< to compare the values.
2) Use the comparison function comp to compare the values.
3,4) Returns the smallest and the greatest of the values in initializer list ilist.
3) Uses operator< to compare the values.
4) Use the comparison function comp to compare the values.
[edit] 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:
bool cmp(const Type1& a, const Type2& b);
While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy(since C++11)).
The types Type1 and Type2 must be such that an object of type T can be implicitly converted to both of them.
[edit] Return value
1,2) Returns the result of
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.
3,4) A pair with the smallest value in 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.
[edit] Complexity
1) Exactly one comparison using operator<.
2) Exactly one application of the comparison function comp.
3,4) Given \(\scriptsize N\)N as ilist.size():
3) At most
\(\scriptsize \frac{3N}{2}\) 3N
2
comparisons using
operator<.
4) At most
\(\scriptsize \frac{3N}{2}\) 3N
2
applications of the comparison function
comp.
[edit] Possible implementation
| minmax (1)
|
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);
} |
| minmax (2)
|
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);
} |
| minmax (3)
|
|
|
| minmax (4)
|
|
|
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
[edit] Example
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <vector>
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:
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
[edit] See also
returns the smaller of the given values
(function template) [edit]
returns the greater of the given values
(function template) [edit]
returns the smallest and the largest elements in a range
(function template) [edit]
returns the smaller and larger of two elements
(algorithm function object)[edit]