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std::min

From cppreference.com
< cpp‎ | algorithm
 
 
Algorithm library
Execution policies (C++17)
Non-modifying sequence operations
(C++11)(C++11)(C++11)
(C++17)
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
(C++11)
Binary search operations
Set operations (on sorted ranges)
Heap operations
(C++11)
Minimum/maximum operations
(C++11)
(C++17)
Permutations
Numeric operations
C library
 
Defined in header <algorithm>
(1)
template< class T >
const T& min( const T& a, const T& b );
(until C++14)
template< class T >
constexpr const T& min( const T& a, const T& b );
(since C++14)
(2)
template< class T, class Compare >
const T& min( const T& a, const T& b, Compare comp );
(until C++14)
template< class T, class Compare >
constexpr const T& min( const T& a, const T& b, Compare comp );
(since C++14)
(3)
template< class T >
T min( std::initializer_list<T> ilist );
(since C++11)
(until C++14)
template< class T >
constexpr T min( std::initializer_list<T> ilist );
(since C++14)
(4)
template< class T, class Compare >
T min( std::initializer_list<T> ilist, Compare comp );
(since C++11)
(until C++14)
template< class T, class Compare >
constexpr T min( std::initializer_list<T> ilist, Compare comp );
(since C++14)

Returns the smaller of the given values.

1-2) Returns the smaller of a and b.
3-4) Returns the smallest of the values in initializer list ilist.

The (1,3) versions use operator< to compare the values, the (2,4) versions use the given comparison function comp.

Contents

[edit] Parameters

a, b - the values to compare
ilist - initializer list with the values to compare
cmp - comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if if a is less than b.

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. ​

Type requirements
-
T must meet the requirements of LessThanComparable in order to use overloads (1,3).
-
T must meet the requirements of CopyConstructible in order to use overloads (3,4).

[edit] Return value

1-2) The smaller of a and b. If the values are equivalent, returns a.
3-4) The smallest value in ilist. If several values are equivalent to the smallest, returns the leftmost such value.

[edit] Complexity

1-2) Exactly one comparison
3-4) Exactly ilist.size() - 1 comparisons

[edit] Possible implementation

First version
template<class T> 
const T& min(const T& a, const T& b)
{
    return (b < a) ? b : a;
}
Second version
template<class T, class Compare> 
const T& min(const T& a, const T& b, Compare comp)
{
    return (comp(b, a)) ? b : a;
}
Third version
template<class T>
T min( std::initializer_list<T> ilist)
{
    return *std::min_element(ilist.begin(), ilist.end());
}
Fourth version
template<class T, class Compare>
T min(std::initializer_list<T> ilist, Compare comp)
{
    return *std::min_element(ilist.begin(), ilist.end(), comp);
}

[edit] Warning

Capturing the result of std::min by reference if one of the parameters is rvalue produces a dangling reference if that parameter is returned:

int n = 1;
const int& r = std::min(n-1, n+1);
// r is dangling

[edit] Example

#include <algorithm>
#include <iostream>
#include <string>
 
int main()
{
    std::cout << "smaller of 1 and 9999: " << std::min(1, 9999) << '\n'
              << "smaller of 'a', and 'b': " << std::min('a', 'b') << '\n'
              << "shortest of \"foo\", \"bar\", and \"hello\": " <<
                  std::min( { "foo", "bar", "hello" },
                            [](const std::string& s1, const std::string& s2) {
                                 return s1.size() < s2.size();
                             }) << '\n';
}

Output:

smaller of 1 and 9999: 1
smaller of 'a', and 'b': a
shortest of "foo", "bar", and "hello": foo

[edit] See also

returns the greater of the given values
(function template) [edit]
(C++11)
returns the smaller and larger of two elements
(function template) [edit]
returns the smallest element in a range
(function template) [edit]