std::max_element

 

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Technical Specifications

 

Algorithm library

Functions
Non-modifying sequence operations
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each countcount_if mismatch equal	findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n removeremove_if remove_copyremove_copy_if	replacereplace_if replace_copyreplace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) unique unique_copy
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is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
Sorting operations (on sorted ranges)
is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
Binary search operations (on sorted ranges)
lower_bound upper_bound	binary_search equal_range
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merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
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is_heap (C++11) is_heap_until (C++11) make_heap	push_heap pop_heap sort_heap
Minimum/maximum operations
max max_element min min_element minmax (C++11) minmax_element (C++11)	lexicographical_compare is_permutation (C++11) next_permutation prev_permutation
Numeric operations
iota (C++11) accumulate inner_product	adjacent_difference partial_sum
C library
qsort	bsearch

 

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

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

Parameters

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 the first argument is less than the second. 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.

Return value

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

Complexity

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

Possible implementation

First version
template<class ForwardIt> ForwardIt max_element(ForwardIt first, ForwardIt last) { if (first == last) { return last; } ForwardIt largest = first; ++first; for (; first != last; ++first) { if (*largest < *first) { largest = first; } } return largest; }
Second version
template<class ForwardIt, class Compare> ForwardIt max_element(ForwardIt first, ForwardIt last, Compare cmp) { if (first == last) { return last; } ForwardIt largest = first; ++first; for (; first != last; ++first) { if (cmp(*largest, *first)) { largest = first; } } return largest; }

Example

Run this code

#include <algorithm>
#include <iostream>
#include <vector>
#include <cmath>
 
static bool abs_compare(int a, int b)
{
    return (std::abs(a) < std::abs(b));
}
 
int main()
{
    std::vector<int> v{ 3, 1, -14, 1, 5, 9 }; 
    std::vector<int>::iterator result;
 
    result = std::max_element(v.begin(), v.end());
    std::cout << "max element at: " << std::distance(v.begin(), result) << '\n';
 
    result = std::max_element(v.begin(), v.end(), abs_compare);
    std::cout << "max element (absolute) at: " << std::distance(v.begin(), result);
}

Output:

max element at: 5
max element (absolute) at: 2

See also

min_element	returns the smallest element in a range (function template)
minmax_element (C++11)	returns the smallest and the largest element in a range (function template)
max	returns the greater of the given values (function template)
std::experimental::parallel::max_element (parallelism TS)	parallelized version of std::max_element (function template)