std::minmax_element

 

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C library
qsort	bsearch

 

Defined in header <algorithm>
template< class ForwardIterator > std::pair<ForwardIterator,ForwardIterator>     minmax_element( ForwardIterator first, ForwardIterator last );	(1)
template< class ForwardIterator, class Compare > std::pair<ForwardIterator,ForwardIterator>     minmax_element( ForwardIterator first, ForwardIterator last,                     Compare comp );	(2)

Finds the greatest and 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.

Parameters

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

Return value

a pair consisting of an iterator to the smallest element as the first element and an iterator to the greatest element as the second. Returns std::make_pair(first, first) if the range is empty. If several elements are equivalent to the smallest element, the iterator to the first such element is returned. If several elements are equivalent to the largest element, the iterator to the last such element is returned.

Complexity

At most max(floor(3/2(N−1)), 0) applications of the predicate, where N = std::distance(first, last).

Possible implementation

First version
template<class ForwardIterator> std::pair<ForwardIterator, ForwardIterator> minmax_element(ForwardIterator first, ForwardIterator last) { typedef typename std::iterator_traits<ForwardIterator>::value_type value_t; return std::minmax_element(first, last, std::less<value_t>()); }
Second version
template<class ForwardIterator, class Compare> std::pair<ForwardIterator, ForwardIterator> minmax_element(ForwardIterator first, ForwardIterator last, Compare comp) { std::pair<ForwardIterator, ForwardIterator> result(first, first);   if (first == last) return result; if (++first == last) return result;   if (comp(*first, *result.first)) { result.second = result.first; result.first = first; } else { result.second = first; } while (++first != last) { ForwardIterator i = first; if (++first == last) { if (comp(*i, *result.first)) result.first = i; else if (!(comp(*i, *result.second))) result.second = i; break; } else { if (comp(*first, *i)) { if (comp(*first, *result.first)) result.first = first; if (!(comp(*i, *result.second))) result.second = i; } else { if (comp(*i, *result.first)) result.first = i; if (!(comp(*first, *result.second))) result.second = first; } } } return result; }

Example

#include <algorithm>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v = { 3, 9, 1, 4, 2, 5, 9 };
 
    auto result = std::minmax_element(v.begin(), v.end());
    std::cout << "min element at: " << (result.first - v.begin()) << '\n';
    std::cout << "max element at: " << (result.second - v.begin()) << '\n';
}

Output:

min element at: 2
max element at: 6

See also

min_element	returns the smallest element in a range (function template)
max_element	returns the largest element in a range (function template)