std::max_element
Defined in header <algorithm>
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template< class ForwardIterator > ForwardIterator max_element( ForwardIterator first, ForwardIterator last ); |
(1) | |
template< class ForwardIterator, class Compare > ForwardIterator max_element( ForwardIterator first, ForwardIterator last, |
(2) | |
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 comp.
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[edit] 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:
The signature does not need to have const &, but the function must not modify the objects passed to it. |
[edit] 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.
[edit] Complexity
Exactly max(N-1,0) comparisons, where N = std::distance(first, last).
[edit] Possible implementation
First version |
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template<class ForwardIterator> ForwardIterator max_element(ForwardIterator first, ForwardIterator last) { if (first == last) { return last; } ForwardIterator largest = first; ++first; for (; first != last; ++first) { if (*largest < *first) { largest = first; } } return largest; } |
Second version |
template<class ForwardIterator, class Compare> ForwardIterator max_element(ForwardIterator first, ForwardIterator last, Compare comp) { if (first == last) { return last; } ForwardIterator largest = first; ++first; for (; first != last; ++first) { if (comp(*largest, *first)) { largest = first; } } return largest; } |
[edit] 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
[edit] 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 larger of two elements (function template) |