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std::minmax(3) C++ Standard Libary std::minmax(3) NAME std::minmax - std::minmax Synopsis Defined in header <algorithm> template< class T > (since C++11) std::pair<const T&, const T&> minmax( const T& a, const (1) (const- expr since C++14) T& b ); template< class T, class Compare > std::pair<const T&, const T&> minmax( const T& a, const (2) (since C++11) T& b, (const- expr since C++14) Compare comp ); template< class T > (since C++11) std::pair<T, T> minmax( std::initializer_list<T> ilist (3) (const- expr since C++14) ); template< class T, class Compare > (since C++11) std::pair<T, T> minmax( std::initializer_list<T> ilist, (4) (const- expr since C++14) Compare comp ); 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. If T is not LessThanComparable, the behavior is undefined. 2) Use the comparison function comp to compare the values. 3,4) Returns the smallest and the greatest of the values in initial- izer list ilist. If ilist.size() is zero, or T is not CopyConstructible, the behavior is undefined. 3) Uses operator< to compare the values. If T is not LessThanComparable, the behavior is undefined. 4) Use the comparison function comp to compare the values. Parameters a, b - the values to compare ilist - initializer list with the values to compare 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 equiva- lent to the following: bool cmp(const Type1& a, const Type2& b); comp - While the signature does not need to have const&, the func- tion 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. 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. 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. 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) 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); } minmax (4) 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); } 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 // Run this code #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: v[2,7]: 4 1 5 9 2 See also min returns the smaller of the given values (function template) max returns the greater of the given values (function template) minmax_element returns the smallest and the largest elements in a range (C++11) (function template) ranges::minmax returns the smaller and larger of two elements (C++20) (niebloid) http://cppreference.com 2024.06.10 std::minmax(3)
NAME | Synopsis | Parameters | Return value | Complexity | Possible implementation | Notes | Example | Possible output: | See also
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