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std::min

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.

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 `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).

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.

Complexity

1-2) Exactly one comparison

3-4) Exactly ilist.size() - 1 comparisons

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); }

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

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

max	returns the greater of the given values (function template)
minmax (C++11)	returns the smaller and larger of two elements (function template)
min_element	returns the smallest element in a range (function template)