std::max

 

C++

Language

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Utilities library

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Algorithms library

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Numerics library

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Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

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
Partitioning operations
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
Set operations (on sorted ranges)
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
Heap operations
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 T > const T& max( const T& a, const T& b );			(until C++14)
template< class T > constexpr const T& max( const T& a, const T& b );			(since C++14)
		(2)
template< class T, class Compare > const T& max( const T& a, const T& b, Compare comp );				(until C++14)
template< class T, class Compare > constexpr const T& max( const T& a, const T& b, Compare comp );				(since C++14)
			(3)
template< class T > T max( std::initializer_list<T> ilist );					(since C++11) (until C++14)
template< class T > constexpr T max( std::initializer_list<T> ilist );					(since C++14)
				(4)
template< class T, class Compare > T max( std::initializer_list<T> ilist, Compare comp );						(since C++11) (until C++14)
template< class T, class Compare > constexpr T max( std::initializer_list<T> ilist, Compare comp );						(since C++14)

Returns the greater of the given values.

1-2) Returns the greater of a and b.

3-4) Returns the greatest of the values in initializer list ilist.

The (1,3) versions use operator< to compare the values, the (2,4) versions use the given comparison function comp.

Parameters

a, b	-	the values to compare
ilist	-	initializer list with the values to compare
comp	-	comparison function object (i.e. an object that satisfies the requirements of Compare) 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 object must not modify the objects passed to it. The types Type1 and Type2 must be such that an object of type T can be implicitly converted to both of them. ​
Type requirements
- T must meet the requirements of LessThanComparable in order to use overloads (1,3).
- T must meet the requirements of CopyConstructible in order to use overloads (3,4).

Return value

1-2) The greater of a and b. If they are equivalent, returns a.

3-4) The greatest value in ilist. If several values are equivalent to the greatest, returns the leftmost one.

Complexity

1-2) Exactly one comparison

3-4) Exactly ilist.size() - 1 comparisons

Possible implementation

First version
template<class T> const T& max(const T& a, const T& b) { return (a < b) ? b : a; }
Second version
template<class T, class Compare> const T& max(const T& a, const T& b, Compare comp) { return (comp(a, b)) ? b : a; }
Third version
template< class T > T max( std::initializer_list<T> ilist) { return *std::max_element(ilist.begin(), ilist.end()); }
Fourth version
template< class T, class Compare > T max( std::initializer_list<T> ilist, Compare comp ) { return *std::max_element(ilist.begin(), ilist.end(), comp); }

Notes

Capturing the result of std::max by reference if one of the parameters is rvalue produces a dangling reference if that parameter is returned:

int n = 1;
const int& r = std::max(n-1, n+1);
// r is dangling

Example

Run this code

#include <algorithm>
#include <iostream>
#include <string>
 
int main()
{
    std::cout << "larger of 1 and 9999: " << std::max(1, 9999) << '\n'
              << "larger of 'a', and 'b': " << std::max('a', 'b') << '\n'
              << "longest of \"foo\", \"bar\", and \"hello\": " <<
                  std::max( { "foo", "bar", "hello" },
                            [](const std::string& s1, const std::string& s2) {
                                 return s1.size() < s2.size();
                             }) << '\n';
}

Output:

larger of 1 and 9999: 9999
larger of 'a', and 'b': b
longest of "foo", "bar", and "hello": hello

See also

min	returns the smaller of the given values (function template)
minmax (C++11)	returns the larger and the smaller of two elements (function template)
max_element	returns the largest element in a range (function template)