std::includes

 

C++

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Algorithm library

Functions
Non-modifying sequence operations
all_of any_of none_of (C++11) (C++11) (C++11) for_each count count_if mismatch equal	find find_if find_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copy copy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n remove remove_if remove_copy remove_copy_if	replace replace_if replace_copy replace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffle shuffle   (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 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>
template< class InputIterator1, class InputIterator2 > bool includes( InputIterator1 first1, InputIterator1 last1,                InputIterator2 first2, InputIterator2 last2 );	(1)
template< class InputIterator1, class InputIterator2 > bool includes( InputIterator1 first1, InputIterator1 last1,                InputIterator2 first2, InputIterator2 last2, Compare comp );	(2)

Returns true if every element from the sorted range [first2, last2) is found within the sorted range [first, last). Also returns true if [first2, last2) is empty.

The first version expects both ranges to be sorted with operator<, the second version expects them to be sorted with the given comparison function comp.

Parameters

first1, last1	-	the sorted range of elements to examine
first2, last2	-	the sorted range of elements to search for
comp	-	comparison function 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 must not modify the objects passed to it. The types  Type1 and  Type2 must be such that an object of type InputIterator can be dereferenced and then implicitly converted to both of them. ​

Return value

true if every element from [first2, last2) is a member of [first, last).

Complexity

At most 2·(N₁+N₂-1) comparisons, where N₁ = std::distance(first1, last1) and N₂ = std::distance(first2, last2).

Possible implementation

First version
template<class InputIterator1, class InputIterator2> bool includes(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2) { for (; first2 != last2; ++first1) { if (first1 == last1 || *first2 < *first1) return false; if ( !(*first1 < *first2) ) ++first2; } return true; }
Second version
template<class InputIterator1, class InputIterator2> bool includes(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp) { for (; first2 != last2; ++first1) { if (first1 == last1 || comp(*first2, *first1)) return false; if (!comp(*first1, *first2)) ++first2; } return true; }

Example

#include <iostream>
#include <algorithm>
#include <cctype>
 
int main()
{
  std::vector<char> v1 {'a', 'b', 'c', 'f', 'h', 'x'};
  std::vector<char> v2 {'a', 'b', 'c'};
  std::vector<char> v3 {'a', 'c'};
  std::vector<char> v4 {'g'};
  std::vector<char> v5 {'a', 'c', 'g'};
  std::vector<char> v6;
 
  for (auto i : v1) std::cout << i << ' ';
  std::cout << "includes:\n";
 
  for (auto i : v2) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v2.begin(), v2.end()) << '\n';
  for (auto i : v3) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v3.begin(), v3.end()) << '\n';
  for (auto i : v4) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v4.begin(), v4.end()) << '\n';
  for (auto i : v5) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v5.begin(), v5.end()) << '\n';
  for (auto i : v6) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v6.begin(), v6.end()) << '\n';
 
  auto cmp_nocase = [](char a, char b) {
    return std::tolower(a) < std::tolower(b);
  }
  std::vector<char> v7 {'A', 'B', 'C'};
  for (auto i : v7) std::cout << i << ' ';
  std::cout << ": "
            << std::includes(v1.begin(), v1.end(), v7.begin(), v7.end(), cmp_nocase)
            << '\n';
}

Output:

a b c f h x includes:
a b c : 1
a c : 1
g : 0
a c g : 0
A B C : 1

See also

set_difference	computes the difference between two sets (function template)
search	searches for a range of elements (function template)