| 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:
The signature does not need to have |
| 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
#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
| returns the smallest element in a range (function template) | |
| (C++11) | returns the smallest and the largest element in a range (function template) |
| returns the greater of the given values (function template) | |
| std::experimental::parallel::max_element
(parallelism TS) | parallelized version of std::max_element (function template) |
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