std::max_element

 

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Defined in header <algorithm>
template<class ForwardIt > ForwardIt max_element( ForwardIt first, ForwardIt last );	(1)
template<class ForwardIt, class Compare > ForwardIt max_element( ForwardIt first, ForwardIt last, Compare comp );	(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.

Parametri

first, last	-	iteratori forward che definiscono l'intervallo di esaminare Original: forward iterators defining the range to examine The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 ForwardIt can be dereferenced and then implicitly converted to both of them. ​
Type requirements
- ForwardIt must meet the requirements of ForwardIterator.

Valore di ritorno

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.

Complessità

Esattamente max(N-1,0) confronti, N =std::distance(first, last) dove.

Original:

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

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Possibile implementazione

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 comp){if(first == last){return last;} ForwardIt largest = first;++first;for(; first != last;++first){if(comp(*largest, *first)){ largest = first;}}return largest;}

Esempio

#include <algorithm>#include <iostream>#include <vector>#include <cmath>   staticbool 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

Vedi anche

min_element	restituisce l'elemento più piccolo in un intervallo Original: returns the smallest element in a range The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione di modello)
minmax_element (C++11)	restituisce l'elemento più piccolo e il più grande in un intervallo Original: returns the smallest and the largest element in a range The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione di modello)
max	restituisce il più grande dei due elementi Original: returns the larger of two elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione di modello)