std::min_element

Defined in header `<algorithm>`
	(1)
template< class ForwardIt > ForwardIt min_element( ForwardIt first, ForwardIt last );			(until C++17)
template< class ForwardIt > constexpr ForwardIt min_element( ForwardIt first, ForwardIt last );			(since C++17)
		(2)
template< class ForwardIt, class Compare > ForwardIt min_element( ForwardIt first, ForwardIt last, Compare comp );				(until C++17)
template< class ForwardIt, class Compare > constexpr ForwardIt min_element( ForwardIt first, ForwardIt last, Compare comp );				(since C++17)

Finds the smallest element in the range [first, last). The first version uses operator< to compare the values, the second version uses the given comparison function comp.

first, last	-	forward iterators defining the range to examine
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); The signature does not need to have const &, but the function object must not modify the objects passed to it. The types Type1 and Type2 must be such that an object of type ForwardIt can be dereferenced and then implicitly converted to both of them.
Type requirements
- `ForwardIt` must meet the requirements of `ForwardIterator`.

[edit] Return value

Iterator to the smallest element in the range [first, last). If several elements in the range are equivalent to the smallest element, returns the iterator to the first such element. Returns last if the range is empty.

[edit] Complexity

Exactly $max(N-1,0)$ comparisons, where N = std::distance(first, last).

[edit] Possible implementation

First version

template<class ForwardIt>
ForwardIt min_element(ForwardIt first, ForwardIt last)
{
    if (first == last) return last;
 
    ForwardIt smallest = first;
    ++first;
    for (; first != last; ++first) {
        if (*first < *smallest) {
            smallest = first;
        }
    }
    return smallest;
}

Second version

template<class ForwardIt, class Compare>
ForwardIt min_element(ForwardIt first, ForwardIt last, 
                            Compare comp)
{
    if (first == last) return last;
 
    ForwardIt smallest = first;
    ++first;
    for (; first != last; ++first) {
        if (comp(*first, *smallest)) {
            smallest = first;
        }
    }
    return smallest;
}

[edit] Example

Run this code

#include <algorithm>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v{3, 1, 4, 1, 5, 9};
 
    std::vector<int>::iterator result = std::min_element(std::begin(v), std::end(v));
    std::cout << "min element at: " << std::distance(std::begin(v), result);
}

Output:

min element at: 1

[edit] See also

max_element	returns the largest element in a range (function template)
minmax_element (C++11)	returns the smallest and the largest element in a range (function template)
min	returns the smaller of two elements (function template)
std::experimental::parallel::min_element (parallelism TS)	parallelized version of `std::min_element` (function template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Technical Specifications